Chapter 6: Common Vegetables for Seed and Fruit

ARTICHOKE OR GLOBE ARTICHOKE AND CARDOON
Cynara scolymus L.,¹³ family Compositae
The artichoke is grown almost entirely in California where there were about 11,000 acres in 1969 with a farm value of about $7 million.
__________
¹³ Cardoon (Cynara cardunculus L.) is similar to artichoke except that it is spiny and more robust. It is cultivated, on a much smaller scale than artichoke, for its edible root and thickened leafstalk. The inflorescence and pollination relationships are similar to artichoke (Bailey 1949*).

Plant:
The artichoke is a herbaceous perennial, the plant being renewed from year to year by lateral offshoots that arise just below the surface of the ground. Each offshoot forms a rosette of leaves, in the center of which the flower stalk later appears. The plant will grow indefinitely, but is usually replaced every 4 to 7 years. It grows to a height of 3 or 4 feet but as much as 6 feet across.

The marketable portion is the 1- to 4-inch immature flower head (fig. 43), including the tender bases and inner portion of the numerous fleshy bracts, the enclosed immature staminal column, and the receptacle or base.

If seed heads are allowed to mature, the flower stalk withers. Propagation is usually vegetative by use of the lateral offshoots or "suckers" (Wellington 1917, Tavernetti 194 7). Propagation by planting seed has been considered impractical (Wellington 1917) because of the variation in the offspring. With improved breeding techniques and development of pure lines, however, the use of planting seed is more practical.

Inflorescence:
The unremoved buds develop centripetally into purple-centered globular flower heads 6 to 8 inches in diameter, resembling those of a gigantic thistle (fig. 44). The numerous 1- to 2-inch long florets, with their slender corolla tubes, are set closely together on the receptacle. The pistil is elongated and conspicuous and appears to be receptive throughout its upper portion (Jones and Rosa 1928*). The anthers discharge their pollen near the stigmatic area of the style, and, according to Foury (1967), the elongating style and stigma take with them a considerable quantity of pollen ready to germinate, but the stigma is not receptive until 5 to 7 days later. By then, the pollen is no longer viable.

[gfx] FIGURE 43. - Artichoke at the proper bud-harvesting stage.
FIGURE 44. - Longitudinal section of artichoke flower, x 1/3, and floret, x 2.

Pollination Requirements:
The pollen must be transferred from anthers of one floret to the stigma of another. According to Harwood and Markarian (1968), pollination is brought about by insects or mechanical agitation of each flower. This indicates that the flower is incapable of self-fertilization, although it is self-compatible. Harwood and Markarian (1968) stated that seed production problems in Russia were reported by Panov (1949).

Pollinators:
Foury (1967) stated that insects are the exclusive pollinators of artichoke. The flowers are freely visited by honey bees and other pollinating insects. Harwood and Markarian (1968) stated that seed yields are uncertain, which they associate with vernalization and weak floral development. The relation of increased pollinating insect population to seed production is not mentioned. The fragmentary information indicates that where maximum seed production is desired, the use of an adequate concentration of pollinating insects would be necessary.

Pollination Recommendations and Practices:
There have been no recommendations for the use of pollinating insects on artichoke, and there is no indication that growers take steps to use such insects.

LITERATURE CITED:
FOURY, C.
1967. [STUDY OF THE FLORAL BIOLOGY OF THE ARTICHOKE (CYNARA SCOLYMUS L.); APPLICATION TO SELECTION. PART 1: DATA ON FLORAL BIOLOGY.] Ann. de l'Amelior. des Plantes 17(4): 357-373. [In French, English summary.]

HARWOOD, R. R., and MARKARIAN, D. HARWOOD, R. R., AND MARKARIAN, D.
1968. ANNUAL CULTURE OF GLOBE ARTICHOKE CYNARA SCOLYMUS L. 1. PRELIMINARY REPORT. Amer. Soc. Hort. Sci. Proc. 92: 400-409.

PANOV, M. A.
1949. [PRODUCING ARTICHOKE SEED.] Sad i Ogorod 12: 55-57. [In Russian.] Cited by Harwood and Markarian (1968)

TAVERNETTI, A. A.
1947. PRODUCTION OF THE GLOBE ARTICHOKE IN CALIFORNIA. Calif. Agr. Ext. Serv. Cir. 76, rev., 19 pp.

WELLINGTON, J. W.
1917. CULTURE OF THE GLOBE ARTICHOKE. N.Y. (Geneva) Agr. Expt. Sta. Bul. 435: 311-319.

ASPARAGUS
Asparagus officinalis L., family Liliaceae
In 1969, asparagus was grown on 123,830 acres in the United States. Almost half, 44,700 acres, was in California; 22,700, in New Jersey; 17,400, in Washington; and 13,900, in Michigan. The crop was valued at $57 million.

Plant:
The underground portion of the perennial, herbaceous asparagus plant is a massive collection of rhizomes and fleshy and fibrous roots. The rhizome sends up a shoot or spear that is harvested when a few inches above ground, otherwise it will continue to develop as an upright flowering stalk or "fern" 4 to 6 feet tall. The stalk develops either female or male flowers, rarely both. If the flower is female, it produces a small round, reddish, 3/8-inch berry that may have a total of two seeds in each of its three locules or six seeds per berry. Frost kills the upright portion of the plant, but the underground portion may live 10 years or more (Henna 1952).

Reproduction is by seeds or by rhizomes called "crowns."

Inflorescence:
The asparagus inflorescence has been variously referred to as pseudohermaphrodite male and pseudohermaphrodite female (Kerner 1897*, p. 299); dioecious, rarely hermaphrodite (Knuth 1909*, p. 464); dioecious, sometimes changing to monoecious (Hexamer 1908); normally dioecious (Jones and Rosa 1928*); and dioecious (Hawthorn and Pollard 1954 *). Intergrades from strongly pistillate to strongly staminate have been observed (Jones and Robbins 1928). In their early stages, the flowers are similar, with both sets of sexual organs present. Later, however, one set usually aborts, leaving a "male" flower with an outer and inner whorl of three stamens each, or a "female" flower with a three-lobed pistil and three-locule ovary, and the other parts rudimentary (fig. 45). Both kinds of flowers have nectaries at the base of the corolla. The individual, whitish-green flowers, from one to four in each axil, are pendulous, bell-shaped, about one-quarter inch long (the male is slightly larger than the female flower) with a characteristic odor (Knuth, 1909*, p. 464). They are freely visited by honey bees and other bees (Norton 1913, Jones and Robbins 1928, Eckert 1956, Pellett 1947*, Jones and Rosa 1928*).

The flowers produce nectar and pollen copiously (Norton 1 913), and beekeepers sometimes get good honey crops from asparagus when the plants are allowed to flower (Pellett 1947*).

[gfx] FIGURE 45. - Longitudinal section of asparagus flower, x 17. A, Female; B, male

Pollination Requirements:
If asparagus seed is to be produced, the pollen must be transferred from the male or staminate flowers to the female or pistillate ones. This transfer must be made between early morning, when the pollen first becomes available, and about noon, when it begins to dry. There should be at least one male plant within 5 feet of each female (Huyskes 1959), about one male for each six female plants.

Pollinators:
Wind is not a factor in asparagus pollination. Bees and primarily honey bees are responsible for the seed crop (Norton 1913, Jones and Robbins 1928, Jones and Rosa 1928*). Eckert (1956) caged one female and two male crowns to exclude all except tiny insects. He harvested only 6.2 g of seed, but an open plant near the cage produced 775 g of seed. He concluded that insect pollination was essential to commercial seed production and that growers should provide one to two colonies per acre to their seed fields for pollination purposes.

Pollination Recommendations and Practices:
There have been no specific recommendations for the use of bees in asparagus seed production except the previously mentioned work by Eckert (1956). Later, he (1959*) made a general recommendation of two colonies per acre for vegetable seed production. There are no reports to indicate that growers take steps to provide insect pollination.

LITERATURE CITED:
ECKERT, J. E.
1956. HONEY BEES INCREASE ASPARAGUS SEED. Amer. Bee Jour. 96: 153-154.

MANNA, G. C.
1952. ASPARAGUS PLANT BREEDING. Calif. Agr. 6(1): 6.

HEXAMER, E. M.
1908. ASPARAGUS, ITS CULTURE FOR HOME USE AND FOR MARKET. 168 pp. Orange-Judd Co., New York.

HUYSKES, J. A.
1959. THE VALUE OF COMPARATIVE TESTS OF PROGENIES FROM OPEN- POLLINATED FEMALE ASPARAGUS PLANTS. Euphytica 8: 141-144.

JONES, H. A., and ROBBINS, W. W.
1928. THE ASPARAGUS INDUSTRY IN CALIFORNIA. Calif. Agr. Expt. Sta. Bul. 446,105 pp.

NORTON, J. B.
1913. METHODS USED IN BREEDING ASPARAGUS FOR RUST RESISTANCE. U.S. Dept. Agr. Burl Plant Ind. Bul. 263,60 pp.

BALSAM-PEAR, BITTER CUCUMBER, OR PERIA
Mormordica charantia L., family Cucurbitaceae
This is a minor crop that occurs in the Old World tropics, but its fruit is much esteemed by Malayans and Chinese. In some areas, it is considered a weed; in others, it is cultivated.

Plant:
Balsam-pear is a slender, smooth, high-climbing, leafy annual that lives about 3 months. Its fruit is oblong or oval, narrowed toward both ends, 4 to 8 inches long, orange-yellow, and covered with blunt warts. The fruit bursts upon maturity showing its scarlet aril surrounding its numerous seeds.

Inflorescence:
The yellow flowers are solitary in the leaf axil, monoecious, or rarely hermaphrodite. The staminate flowers are 1 to 1 1/2 inches long, the pistillate ones slightly smaller. Flower opening is similar to our cucumber.

Pollination Requirements:
The pollen must be transferred from the staminate to the pistillate flowers. Pollinators In Kuala Lampur, this plant is pollinated by small bees (Sands 1928).

Pollination Recommendations and Practices:
None.

LITERATURE CITED:
SANDS, W. N.
1928. THE BITTER-CUCUMBER OR PERIA. Malayan Agr. Jour. 16(2): 32.

BEET
Beta vulgaris L., family Chenopodiaceae
The term "beet" is used to include both the garden beet and sugar beet grown in the United States. The former were grown on 17,930 acres in 1969 and were valued at $4.8 million; the latter were grown on about 1.5 million acres with a farm value of $353 million.

Plant:
The beet is normally an herbaceous biennial. The first year it develops a rosette of large leaves and a fleshy root. The second year it develops a seed-stem, which draws upon the food stored in the root, and after the seed crop is produced the entire plant dies. The whitish root of the sugar beet (from which sugar is obtained) may be 6 to 8 inches thick and up to 2 feet long. The reddish garden beet root is more or less oval and 2 to 4 inches across. The leaf of the sugar beet rosette may reach 2 feet high by 6 to 8 inches across. The garden beet leaves are much more delicate. Whether the plant is grown for its root as a vegetable or as a source of sugar, the growth characteristics are similar. The second year the seed-stem appears and a seed crop is obtained. Both types of beets are cultivated in rows.

Inflorescence:
The many-branched seed stem, which produces the inflorescence and which may reach 4 to 6 feet, is composed of large particulate open spikes. The small, greenish, sessile flowers (fig. 49) are usually in clusters of two or three, one of which bears a single, extended bract. The flowers are perfect although they rarely self, because the stigma is not fully mature when the flower opens (Artschwager 1926). The flower opens in the morning, and the anthers dehisce before noon. The stigmatic lobes open gradually in the afternoon and are not fully open until the second or even the third day. By then, the anthers of the same flower have shriveled and no longer produce pollen. Once open, the stigma may then be receptive for more than 2 weeks. Shaw (1914) indicated that a pungent nectar is present and that there is an abundance of pollen. Jones and Rosa (1928*) also reported that a large amount of pollen is produced, which is carried long distances by wind. Meier and Artschwager (1938) reported that beet pollen was collected by airplane 5,000 m above beet fields.

[gfx] FIGURE 49. - Longitudinal section of beet flower, x 33.

Pollination Requirements:
Poole (1937) stated that the beet is an example of a wind-pollinated species that is also insect pollinated to some extent. Shaw (1916) stated that self-incompatibility seemed to be the general rule in beets. Owens (1945) reported that male-sterility existed in sugar beets. Mikitenko (1959) trained bees to collect nectar from beets, which resulted in an increase in seed production of 14.3 percent compared with the control. Stewart (1946) concluded that wind alone is sufficient to transfer the pollen from anthers to stigmas, but unfortunately the conclusion was based on production of plants in the open compared to plants in cages that excluded larger insects. No attention was paid to "larger insects" on the open plants or to small insects in the cages.

Although beets are basically wind pollinated, some benefit may be derived from insect pollination. The lengthy period that the stigma is receptive to pollen doubtless contributes to the chances that windborne pollen will encounter it in time to effect fertilization and the production of seed.

Pollinators:
Wind is doubtless the major pollinating agent of beets. However, Shaw (1914) reported that thrips cross-pollinate some flowers. Treherne (1923) considered syrphids the most prevalent cross-pollinating insects present on beet flowers, but honey bees, solitary bees, and various Hemiptera were also important. Sharma and Sharma (1968) reported that honey bees were "prominent" on sugar beet flowers. Popov (1962) (according to Free 1970*) stated that Halictidae, Megachilidae, and Anthophoridae were most abundant on beet flowers. Mikitenko (1969) and Archimowitsch (1949) reported that bees will visit beets in large numbers for pollen if nothing else is available, and Mikitinko (1969) stated that they may increase yield of beet seeds. The finding of numerous honey bees or wild bees on beet flowers in the United States is unlikely if there is other pollen available in the area.

Pollination Recommendations and Practices:
Although the evidence indicates that pollinating insects may cause some increase in beet seed yields, their value is given no consideration in the usual recommendations for beet seed production. The evidence indicates that they may be beneficial, and for that reason their activity in flowering beet fields should be encouraged.

LITERATURE CITED:
ARCHIMOWITSCH, A.
1949. CONTROL OF POLLINATION IN SUGAR BEETS. Bot. Rev. 15: 613-628.

ARTSCHWAGER, E.
1926. DEVELOPMENT OF FLOWERS AND SEED OF SUGAR BEETS. Jour. Agr. Res. 34: 1-25.

MEIER, F. C., and ARTSCHWAGER, E.
1938. AIRPLANE COLLECTION OF SUGAR BEET POLLEN. Science 88: 507-508.

MIKITENKO, A. S.
1959. [BEES INCREASE THE SEED CROP OF SUGAR BEET.] Pchelovodstvo 36(5): 28-29. [In Russian.] AA-356/60.

OWENS, F.V.
1945. CYTOPLASMTCALLY INHERITED MALE-STERILITY IN SUGAR BEETS Jour. Agr. Res. 71: 423-440.

POOLE, C. F.
1937. IMPROVING THE ROOT VEGETABLES. U.S. Dept. Agr. Yearbook 1937: 300-325.

POPOV, V. V.
1952. [APIDAE POLLINATORS OF CHENOPODIACEAE.] Zool. Zhur. 31: 494-503. [In Russian] , Cited by Free (1970 *).

SHARMA, P. L., and SHARMA, B. R.
1968. ROLE OF INSECTS IN THE POLLINATION OF DAUCUS CAROTA (CARROTS) AND BETA VULGARIS (SUGAR BEET). Indian Jour. Hort. 25(3/4): 216.

SHAW, H. B.
1914. THRIPS AS POLLINATORS OF BEET FLOWERS. U.S. Dept. Agr. Bul. 104, 12 pp.

_____ 1916. SELF, CLOSE AND CROSS-FERTILIZATION OF BEETS. N.Y. Bot. Garden Mem. 6: 149-152.

STEWART D.
1946. INSECTS AS A MINOR FACTOR IN CROSS POLLINATION OF SUGAR BEETS. Amer. Soc. Sugar Beet Tech. Proc. 4: 256-258.

TREHERNE, R. C.
1923. THE RELATION OF INSECTS TO VEGETABLE SEED PRODUCTION. Quebec Soc. Protect. Plants Ann. Rpt. 15: 47-59.

BROCCOLI
(See "Cole Crops")
BRUSSELS SPROUT
(See "Cole Crops")
CARROT
Daucus carota L., family Umbelliferae
Carrots were grown on 78,530 acres in the United States in 1969, with a farm value of $82,967,000. The seeds, about a million pounds, were produced on about 2,000 acres, primarily in California, Idaho, and Oregon (Whitaker et al. 1970).

Plant:
When grown for seed (fig. 62), two methods may be employed. If the seed-to-seed method is used, the seeds are planted in the late summer, the root overwinters in the soil, and the following year the growth produces a seed crop. In the root-to-seed method, the roots or stecklings are removed from the soil in the fall, stored at 33 deg F until the following spring, then transplanted, and the seed crop is harvested from the plant in the fall. In both instances, the crop is grown in rows and cultivation is necessary. Franklin (1948) concluded that proper storage of stecklings was the greatest single problem in carrot seed production.

[gfx]
FIGURE 62.- Carrot seed field about ready to harvest.

Inflorescence:
The inflorescence, typical of the umbelliferae, consists of a terminal or primary compound umbel of white flowers, 5 to 6 inches across, and a system of second-, third-, and fourth-order umbels, named in relation to their appearance on the plant below the primary umbel. The umbels decrease in size as the order number increases. The first and fourth order umbels are of little importance in seed production (Borthwick 1931). The individual flower is usually perfect (Knuth 1909*, p. 502), although Braack and Kho (1958) reported that a tendency to produce only male flowers occurs and with increasing frequency in the umbels of high orders. A flower normally has five functional stamens and two styles, which lead to the two locules of the ovary. Each locule contains a single ovule, thus two seeds per flower from flowers in a room free of harmful insects and supplied with flies to pollinate the flowers.

Nectar is secreted from a swollen disk on the upper surface of the ovary and is easily available to all types of insects. Pellett (1947*) reported that 100,000 to 150,000 pounds of honey is produced from carrots annually, but its quality is poor. Carrot pollen is attractive to numerous insects (Bohart and Nye 1960). Gary et al. (1972) showed that carrot blossoms were much more attractive to honey bee pollen collectors than onion blossoms, as only 7 percent of the visitors to onion flowers were collecting pollen compared with 66 percent of the visitors to carrot blossoms. Flowering extends over about a month, and dehiscence within an umbel covers about 7 days. Within a floret, the anthers dehisce over a 1-to 2-day period, the stigma receptivity begins on the third or fourth day. The stigma may remain receptive a week or possibly longer ( Hawthorn and Pollard 1954*, Hawthorn et al. 1960, Franklin 1953, Poole 1937).

Pollination Requirements:
Jones and Rosa (1928*) and Enzie (1943) stated, without supproting data, that carrots were "mostly insect- pollinated." Rather thorough studies of carrot pollination were made by Hawthorn et al. (1960) (fig. 63). By comparing production from open plots with that from plots caged (a) to exclude all insects, (b) to exclude all but tiny insects, or (c) to enclose a colony of honey bees, they proved that insect pollinators were essential for commercial seed production. In cages excluding all insects, an averae of only 128 pounds of seed per acre was produced. When tiny insects were permitted to visit the flowers 453 pounds of seed per acre developed, open plots exposed to pollinators in the area yielded 711 lb/acre. Hawthorn et al. (1960) concluded from their close studies of the 'Red Core Chantenay' cv. that "limited but significant opportunity existed for self-pollination from one umbellet to another by jarring or wind action, and a greater opportunity ( on a time basis) for cross- pollination by accidential rubbing together of umbels on adjacent plants."

However, their test established that such self or mechanical pollination in the absence of pollinating insects was of little value in the comercial production of seed. Slate (1927) concluded that only about 15 percent of the carrot plants set seed from their own pollen. Even though apparently only two pollen grains are essential in the fertilization of the two ovules of the flower, and the stigma is receptive to pollen either from flowers of the same plant or from others for as much as a week, Paci (1956), Pankratova (1957), and Hawthorn et al. (1960) concluded that there is sufficient transfer of such pollen without pollinating insects. Thompson (1962) reported that more than 95 percent crossing occurred in the field at Ithaca, N.Y., but he gave no indication as to the pollinating agents.

The value of hybrid vigor in carrots has been known for years (Poole 1937) and male sterility, essential in its utilization, was reported shortly thereafter (Welch and Grimball 1947), but only a few hybrids have been produced commercially. Whitaker et al. (1970) stated that the uniform, smooth, highly colored roots produced by superior hybrids cannot be duplicated by the open-pollinated varieties. However, hybrid carrot seed production is so recent that time has not permitted the identification of problems that might be involved in providing adequate cross-pollination for this crop. The relatively long flowering period of carrots is favorable and so is the attractiveness of both the nectar and pollen to a broad spectrum of pollinators, particularly honey bees. For large-scale production of seeds, however, where male-sterile plants are used, there is need for pollinating agents interested only in nectar collection that will freely cross over from the normal to the male-sterile flowers and effect maximum cross-pollination.

[gfx]
FIGURE 63.- Carrot pollination studies, showing flowers tagged to indicate mode of pollination.

Pollinators:
Associated with the studies made by Hawthorn et al. (1960) on the need for insect pollinators, Bohart and Nye (1960) also studied the insect visitors to carrot flowers. They collected on the carrot blossoms 334 species of insects representing 71 families, which in itself shows the attractiveness of these blossoms to a wide variety of insect visitors. Most of the species of visitors were in the superfamily Apoidea, or the Ichneumonidae, Psammocharidae (Pompilidae), Sphecidae, and Vespidae families of the Hymenoptera, and the Bombyliidae, Sarcophagidae, Stratiomyidae, Syrphidae, and Tachinidae families of the Diptera. Bohart and Nye (1960) proposed an efficiency rating for the insect pollinators of carrots, based on the amount of loose pollen on the insects' body, the size of the insect, and its activity on the flower head. By multiplying this rating figure by the numbers of insects observed on the flowers, a pollination index was obtained for each species.

They concluded that several genera in the Apoidea were important pollinators of carrots, but from the practical standpoint the honey bee was the only species that could be manipulated and utilized in commercial seed production (fig. 64).

Pankratova (1958) reported that the chief pollinators of carrots near Moscow were flies (90 percent) and bees (9 percent). No mention was made of the number of honey bee colonies in the area nor the plant competition.

The activity of honey bees on carrot blossoms was studied by Bohart and Nye (1960). They stated that pollen collecting honey bees "literally wade across the heads, swinging their abdomens back and forth and scraping the pollen from stamens with their forelegs. The nectar collectors stand higher on the flowers, move about less, and lap up droplets from the exposed nectaries. In other species of bees, the females usually behave like pollen-collecting honey bees and the males like nectar-collecting honey bees."

Hawthorn et al. (1960) reported that plants caged to exclude pollinating insects apparently reached their peak of bloom a few days earlier and held it more than a week longer than plants in the open or in cages where bees were present. This difference, however, was attributable to the dislodging of petals by bees and was only an "illusion" so far as actual flowering was concerned.

As shown earlier by Hawthorn et al. (1960), bees increased production of carrot seed. As a result of the bee activity, there were fewer undesirable large seed and they matured more rapidly and germinated better than seeds produced where the pollinator level was low. Also, progressive shrinkage in weight of seeds, which following the various cleaning processes, was accelerated with every decrease in pollination level. Both quantity and quality of carrot seeds are improved by high levels of bee pollination. Franklin (1970) reported that at one time in Parma, Idaho, the carrot fields were teeming with bees, and excellent seed crops were obtained. Then pest control methods and materials changed, competitive crops moved in, bee counts dropped, and the seed crops failed.

[gfx]
FIGURE 64.- Honey bee collecting nectar from carrot flower.

Pollination Recommendations and Practices:
As a result of their studies Bohart and Nye (1960) made the following recommendations: "(1) Locate enough colonies of honey bees in the area to provide effective populations on the flower heads; (2) avoid the presence of competing bloom; (3) restrict plantings of carrots for seed to avoid dilution of the pollinator population; (4) choose areas with varied habitats capable of supporting large numbers of a wide variety of pollinators; (5) take steps to increase populations of wild pollinators in the area. For most large seed-producing areas a combination of the first and second methods is likely to prove the most practical."

Hawthorn et al. (1960) gave a little more indication as to the number of pollinators needed. They stated, "Under the cultural conditions of our experiments, a honey bee population of 8 per square yard (the lowest average number for the season in our cages) is apparently as high as the plant can use to advantage. Probably a somewhat smaller number would do just as well, although we have no direct evidence to support such a conclusion."

Pankratova (1957) stated that the most reliable pollinators of carrots are honey bees. He recommended transporting colonies to the field, but the number of colonies was not mentioned. Hawthorn et al. (1956) also recommended movement of colonies of honey bees to carrot fields to provide the large numbers necessary at flowering time but did not designate the number. Naturally, the number needed would be influenced by competition from other flowers, the strength and condition of the colonies, and the attractiveness of the carrot flowers. Under most conditions where carrots are grown for seed and maximum production is desired, the placement of several colonies per acre in and around the field would probably be justified. Eight bees per square yard of flowers should be striven for regardless of the number of colonies required to provide this.

LITERATURE CITED:
BOHART, G. E., and NYE, W. P.
1960. INSECT POLLINATORS OF CARROTS IN UTAH. Utah Agr. Expt. Sta. Bul. 419, 16 pp.

BORTHWICK, H. A.
1931. CARROT SEED GERMINATION. Amer. Hort. Sci. Soc. Proc. 28: 310-314.

BRAAK, J. P., and KHO, Y. O.
1958. SOME OBSERVATIONS ON THE FLORAL BIOLOGY OF THE CARROT (DAUCUS CAROTA L.). Euphytica 7(2): 131-139.

ENZIE J. V.
1943. EXPERIMENTS IN THE PRODUCTION OF CARROT SEED. N. Mex. Agr. Expt. Sta. Bul. 308, 11 pp.

FRANKLIN, D. F.
1948 SOME PROBLEMS IN CARROT SEED PRODUCTION. Seed World 63(8): 8-9, 44.

FRANKLIN, D. F.
1953. GROWING CARROT SEED IN IDAHO. Idaho Agr. Expt. Sta. Bul. 294, 35 pp.

______ 1970. PROBLEMS IN THE PRODUCTION OF VEGETABLE SEED. In The Indispensable Pollinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp. 112-141.

GARY, N. E., WITHERELL, P. C., and MARSTON, J.
1972. FORAGING RANGE AND DISTRIBUTION OF HONEY BEES USED FOR CARROT AND ONION POLLINATION. Environmental Ent. 1(1): 71 - 78.

HAWTHORN, L. R., BOHART, G. E., and TOOLE, E. H.
1956. CARROT SEED YIELD AND GERMINATION AS AFFECTED BY DIFFERENT LEVELS OF INSECT POLLINATION. Amer. Soc. Hort. Sci. Proc. 67: 384 - 389.

______BOHART, G. E, TOOLE, E. H., and others.
1960. CARROT SEED PRODUCTION AS AFFECTED BY INSECT POLLINATION. Utah Agr. Expt. Sta. Bul. 422, 18 pp.

PACI, P.
1956. [RESEARCH ON THE FLORAL BIOLOGY OF THE CARROT.] Riv. Ortoflorofruttic. Ital. 40: 414-423. [ln Italian, English summary.]

PANKRATOVA, E. P.
1957. [THE EFFECT OF BEE POLLINATION ON THE HARVEST OF CARROT SEED.] Dokl. TSKha 30 (part 2): 332-336. [ In Russian. ] AA-396/61.

______ 1958. [DATA ON THE BIOLOGY OF BLOSSOMING AND POLLINATION OF CARROTS.] Dokl. TSKha 36: 118 - 123. [In Russian.] AA-727/62.

POOLE C. F.
1937. IMPROVING THE ROOT VEGETABLES. U.S. Dept. Agr. Yearbook 1937: 300-325.

SLATE, W. L.
1927. REPORT OF THE DIRECTOR. Conn. Agr. Expt. Sta. Bul. 291: 91-111.

THOMPSON, D. J.
1962 NATURAL CROSS-POLLINATION IN CARROTS. Amer. Soc. Hort. Sci. Proc. 81: 332 - 334.

WELCH, J. E., and GRIMBALL, E. L., JR.
1947. MALE STERILITY IN THE CARROT. Science 106: 594.

WHITAKER, T. W., SHERF, A. F., LANGE, W. H., and others.
1970. CARROT PRODUCTION IN THE UNITED STATES. U.S. Dept. Agr., Agr. Handb. 375, 37 pp.

CAULIFOWER
(See "Cole Crops")
CELERIAC
Apium graveolens L. var. rapaceum (Mill.) DC, family Umbelliferae
Celeriac, often called knob-celery, is grown primarily for its roots (fig. 67), which are similar to turnips but with a celery flavor (James 1965). Otherwise, so far as is known, its pollination requirements are the same as for celery (see "Celery"). Its culture for seed resembles that of carrot (see ''Carrot'') (Hawthorn and Pollard 1956*).

[gfx]
FIGURE 67. - Celeriac roots.

LITERATURE CITED:
JAMES, R. 1965. CELERIAC - CELERY WITH A DIFFERENCE. Organic Gard. and Farming 12(2): 75.

CELERY
Apium graveolens L. var. dulce (Mill.) DC, family Umbelliferae
In 1970, celery was grown on 31,980 acres, about half of which was in California with Florida second in production. The crop was valued at $85,657,000. The seed was produced primarily in California although some was produced in Michigan, Idaho, and Utah (Hawthorn and Pollard 1954 *). Under ideal growing conditions, 3,000 pounds of seed per acre can be produced (Watson 1943). The acreage devoted to seed production was small - 100 to 200 acres (Hawthorn and Pollard 1954*).

Plant:
The celery plant is a many-branched glabrous biennial. The first year it develops an upright rosette of leaves with ribbed petioles to 2 feet. This part is harvested as a vegetable. If seed is desired, the plants are left until fall or winter, depending upon the location, then the roots are dug, and stored until spring when they are re-set in another location in 3- foot rows and about 3 feet apart in the row. The plant is then allowed to develop its grooved and jointed flowering stalk about 3 feet high.

Inflorescence:
The inflorescence is a series of umbels and umbellets, smaller and less compact than those of the carrot (fig. 68). The small white flowers are arranged in whorls, the outer ones opening first with successive whorls opening over a period of several days. The individual flower opens in the early morning and the anthers dehisce shortly afterwards, sometimes before the petals have fully spread. The afternoon of the following day the petals fall. On the third day, the style begins to rise but is not fully erect until the evening of the fifth day. From about then until about the eighth day, the stigma is covered with stigmatic fluid and is receptive to pollen (Emsweller 1928). Celery in bloom is strong smelling but yields abundant nectar and is highly attractive to bees (Root 1919).

[gfx] FIGURE 68. - Portion of celery stalk, showing leaves and flowering stem

Pollination Requirements:
The individual flower is self-fertile but incapable of self- pollination, since the pollen is shed and dissipated before the stigma is receptive. The flowers are receptive to pollen of the same plant (Jones and Rosa 1928*), but the pollen must be transferred from the anthers to receptive stigmas of other flowers by insects.

Pollinators:
Because of the attractiveness of the flowers to honey bees, these insects are probably the most satisfactory as pollinating agents, provided they are present in sufficient abundance. No information is available on the desirable population density of pollinators on celery, but the eight bees per square yard suggested for carrots (Hawthorn et al. 1960) should be satisfactory.

Pollination Recommendations and Practices:
No recommendations have been made on the use of pollinating insects on celery, probably because of the small acreage devoted to seed production.

LITERATURE CITED:

EMSWELLER, S. L.
1928. POLLINATION AND FERTILIZATION OF CELERY. Amer. Soc. Hort. Sci. Proc., pp. 29 - 30, 25th Ann. Mtg.

HAWTHORN, L. R., BOHART, G. E., TOOLE, E. H., and others.
1960. CARROT SEED PRODUCTION. Utah Agr. Expt. Sta. Bul. 422,18 pp.

ROOT E. R.
1919. ALONG THE SACRAMENTO RIVER HONEY FROM PARSNIPS AND CELERY BY THE CARLOAD IN CALIFORNIA. Gleanings Bee Cult. 47: 711-713.

WATSON, M.
1943. THE CULTURE OF CARAWAY AND CELERY SEED IN CALIFORNIA. Calif. Hort. Soc. Jour. 4: 9 - 13.

CHAYOTE
Sechium edule (Jacq.) Swartz, family Cucurbitaceae
Chayote is also called Christophine (Purseglove 1968*), mirliton and tayote (Cook 1901), and trellis squash (Fairchild 1947). It is a cucurbit crop of minor importance, comparable to the gherkin and citron melon (Hawthorn and Pollard 1954*). It is grown in Australia, Guatemala, Mexico, Puerto Rico, and other subtropical countries. Bukasov (1930) reported that chayote was very common in Mexico and Guatemala below 6,600 feet. It has been grown in Louisiana, mainly in home gardens around New Orleans, and there was one small commercial planting in Florida in 1971 (D. O. Wolfenbarger, personal commun., 1971).

Plant:
Chayote is a robust, climbing, or sprawling herbaceous perennial with tuberous roots and with vines up to 12 yards long. It resembles a cucumber but is much more vigorous. It prefers shelter from wind and a place to climb (Whitaker and Davis 1962*). The leaves are strongly three- angled, rough textured, and deep green with white veins. The plant grows best at altitudes above 1,000 feet in the tropics in areas of moderate rainfall, but will grow wherever the soil does not freeze and there is sufficient moisture. The top is killed by frost.

The green, jade, or white ivory fruit is similar in shape and size to the avocado (fig. 69), with a single short-lived seed. The fruit is an excellent substitute for summer squash, the roots are comparable to yams, the young leaves are eaten like spinach, and the shoots are acceptable substitutes for asparagus tips.

Whitaker and Davis (1962*) stated that the cultivars are not clearly separated but are identified largely by the type of fruit such as the cvs. 'Round White', 'Long White', 'Pointed Green', 'Broad Green', or 'Oval Green'. The plant requires day lengths slightly over 12 hours before flowering can begin. For this reason, they do not flower in temperate regions before fall. The fruit reaches full size 30 days after anthesis. The entire fruit, with its single seed, is planted when a new plant is desired. Chayote yields 25 to 100 fruits per plant, averaging 1 pound each.

[gfx] FIGURE 69. - Complete and sectioned chayote fruit.

Inflorescence:
Cook (1901) stated that the l/4 to l/2-inch five-petal pistillate flower is solitary, otherwise it is not different from the more numerous staminate blossoms. The ovary is one-celled with one ovule. Knuth (1908*, p. 454, 458), citing Arcangeli, stated that there are two nectaries in both male and female flowers at the base of each of the five lobes of the corolla, 10 per flower. In the male, these nectaries form small narrow inconspicuous pockets, but in the female flowers they are larger and more conspicuous. The explanation offered was that insect visitors find only nectar in the female flowers, therefore the nectary must be more attractive, whereas both pollen and nectar are found in the male flowers. Cook (1901) reported that the vines swarmed with bees and the plant was a good honey producer. He also stated that, in the United States, fields of chayote were recognized as good bee pasture, seemingly making up in numbers what the flower lacked in size. Pellett (1947*) listed chayote as a valuable honey plant. It blooms continually if not killed by frost. Wulfrath and Speck (n.d.) considered it a wonderful source of nectar.

Pollination Requirements:
Other than that the plant is monoecious, having staminate and pistillate flowers that are insect pollinated, little seems to be known about the pollination of chayote. Because only a single ovary and seed occurs within a flower, repeated visits by bees to a flower may not be necessary. Fairchild (1947) stated that when the flower is fertilized and fruit sets, it grows rapidly to maturity.

Pollinators:
Where honey bees are attracted to the flowers in sufficient numbers, additional steps to provide pollination is unnecessary. If production is on a big scale, there might be more flowers than the local supply of insects could pollinate. Should that occur, some provision for additional bees should be made.

Pollination Recommendations and Practices:
No recommendations for the use of pollinating insects on chayote have been made.

LITERATURE CITED:
ARCANGELI, C.
1892. [SULL'IMP0LLINAZIONE IN VARIE CUCURBITACEE E SUI L0RO NETTARII.] Atti del Congresso Bot. Internaz. 1892, pp.441-454. Genoa. [ In Italian. ]

BUKASOV, S. M.
1930. THE CULTIVATED PLANTS OF MEXICO, GUATEMALA, AND COLOMBIA. Bul. Appl. Bot., Genet., and Plant Breeding Sup. 47: 1 - 553. [In Russian, pp. 470 - 553 in English.]

COOK, O. F.
1901. THE CHAYOTE: A TROPICAL VEGETABLE U.S. Dept. Agr. Div. Bot. Bul. 28, 31 pp.

FAIRCHILD, D.
1947. EARLY EXPERIENCES WITH THE CHAYOTE. Fla. State Hort. Soc. Proc. 60: 172-178.

WULFRATH, A., and SPECK, J. J.
[n.d.] [LA FLORA MELIFERA.] Enciclopedia Apicola, Folleto 28. Ed. 2. 96 pp. Ediciones Mexicanas, Mexico, D.F. [In Spanish.]

CHICORY
Cichorium intybus L., family Compositae
Chicory, also known as succory, is cultivated to a limited degree as a salad or potherb, or its taproot is roasted, ground, and used as a coffee substitute or admixture (Purseglove 1968*). It is also grown in some countries for alcohol distillation from the roots. (Davidovich and Davydova 1947).

Plant:
Chicory is a stout, deep-rooted perennial, 3 to 6 feet tall. It is a practically leafless herb, branching and diffuse when in bloom. The seeds are planted in the spring, and the roots are dug in the fall, stored, and replanted toward spring for foliage harvest (Jones and Rosa 1928*). The plant is most noticeable in the mornings when its azure-blue flowers are open.

Inflorescence:
The composite 1 1/2 inch flower opens early in the morning (5:30 to 7:30 a.m.) and closes about noon (Dinakaran and Sundaraj 1960). It contains 20 to 30 drab disk flowers and about 12 beautiful, l/2-inch-long, blue ray flowers. When the floret opens, the style covered with sweeping hairs extrudes through the short anther tube then twists into a one- or two-coil spiral; when this occurs, the stigma comes in contact with the pollen on the sweeping hairs (Test 1967). This pollen, along with the nectar at the base of the corolla tube is available to bees and many other nectar- and pollen- feeding insects. Pellett (1947*) stated that chicory is a good source of pollen and nectar for honey bees and that the bees produce from chicory a yellowish-green honey.

Pollination Requirements:
Knuth (1908*, p. 672) stated that when the stigma comes in contact with the pollen adhering to the style, automatic self-pollination occurs in the absence of insects. Rick (1953) found that self-pollination was unsuccessful because chicory is self-incompatible. Stout (1916) selfed plants and obtained no seeds, but his open-pollinated plants set 61 percent of the flowers, which also showed that the plants were self- incompatible. Dinakaran and Sundara; (1960) stated that fertilization occurs both within and between heads as a result of insect activity. Pecant (1958) found all stages of compatibility in each cultivar studied, indicating that seed production would be materially benefited by pollinating insect activity. Davidovich and Davydova (1947) conducted cage tests with two cultivars, 'Magdeburg' and 'Golova Ugrya', and the data below, taken from their report, shows that both cultivars benefited from insect pollination. Both cultivars had only a few empty achenes if bees were present, but many if bees were absent.

[gfx]
__________________________________________________________ ÔMagdebuurgÕ ÔGolova UgryaÕ cv. Exposure to pollinators Full Puny Empty Full Puny Empty __________________________________________________________ Percent of achenes Caged with bees 61.4 22.7 15.9 50.0 40.5 9.5 Open 59.5 4.3 36.2 43.3 30.7 26.0 Caged without bees 14.7 5.0 80.3 10.3 7.9 81.8 __________________________________________________________

Davidovich and Davydova (1947) also observed trees in two open fields, one of which was 300 m from the apiary and one 3 km away. Near the apiary, 12 bees per 10 m² resulted in 11 g seed per plant; whereas at the distant location where only six bees per m2 were observed, only 7 g of seed per plant were obtained. The results showed that about 1 bee per square yard resulted in almost twice as much seed as one-half bee per yd2. This showed the value of and need for bee pollinators for commercial production of chicory seed.

Pollinators:
There seems to be little information on the pollinating agents of chicory other than honey bees. The type of flower and its relationship to other better known plant species would indicate that it is not wind pollinated. This is supported by the data obtained in the above experiment by Davidovich and Davydova (1947). Knuth (1908*, p. 672) mentioned numerous insect visitors in the Coleoptera, Diptera, Lepidoptera, and Hymenoptera. Within the Hymenoptera, he mentioned the genera Andrena, Anthidium, and Apis; and many spp. of Halictus, Osmia, and Prosopis. Of these insects, only the honey bees have been demonstrated to be effective, and they can be concentrated on the crop effectively when and where desired.

Pollination Recommendations and Practices:
None.

LITERATURE CITED:
DAVIDOVICH, K, A., and DAVYDOVA, N. S.
1947. [CHICORY AND HONEY BEES.] Pchelovodstvo 24(1): 26 - 28. [In Russian.]

DINAKARAN, M., and SUNDARAJ, D. D.
1960. PRELIMINARY STUDIES ON CHICORY (CICHORIUM INTYBUS L.) WITH SPECIAL REFERENCE TO FLORAL BIOLOGY. So. India Hort. 8: (1/2): 23-27.

PECANT, P.
1958. NOTE SUR LA BIOLOGIE FLORAL DE L'ENDIVE (CICHORIUM INTYBUS) AUTO-COMPATABILITE ET INTER-INCOMPATIBILITE. Adv. in Hort. Sci. and Their Appl. 15th Internatl. Hort. Cong. Proc. Nixe 1: 376-380. [In French, English abstract.]

RICK, C.M.
1953. CHICORY-ENDIVE HYBRIDIZED. Calif. Agr. 7(9): 7.

STOUT, A. B.
1916. SELF- AND CROSS-POLLINATION IN CICHORIUM INTYBUS WITH REFERENCE TO STERILITY. N.Y. Bot. Gard. Mem. 6: 333 - 454.

TEST, R.
1967. [FLORAL BIOLOGY AND REPRODUCTION IN CHICORY.] Sementi Elette 13(1): 22 - 27. [In Italian, English summary.]

CHIVE
Allium schoenoprasum L., family Amaryllidaceae
Chive (see "Onions") seeds are produced in limited quantities in the United States because the plant can also be propagated vegetatively. Even so, chives are not grown to any great extent. The leaves are used in fresh salads and for flavoring of other foods.

Plant:
Chives are perennial plants, much smaller than onions, and they grow in compact clumps or clusters. The leaves are about one-fourth the size of onion leaves. The seedstalk is short and, after the first year, appears annually (Hawthorn and Pollard 1954*).

Inflorescence:
The 1-foot-tall chive inflorescence has only 25 to 100 florets, and when seeds are produced, many shatter. It is considered to be a "shy" or poor seed producer.

Pollination Requirements:
Knuth (1909*, p. 457) stated that the flowers are feebly protandrous. The anthers release their pollen slightly before the stigma becomes receptive, and the flowers close at night so that self-pollination is possible if insect pollination fails. Kropacova et al. (1969) indicated that chives, like onions, require bee pollination.

Pollinators:
Kropacova et aL (1969) reported that honey bees were the primary pollinators of chives. They indicated an insufficiency of bees on the older plants.

Pollination Recommendations and Practices:
None.

LITERATURE CITED:
KROPACOVA, S., KROPAC, A., and NEDBAL0VA, V.
1969. [STUDIES OF THE RELATIONSHIP BETWEEN FL0WER POLLINATION AND SEED FORMATION IN THE CHIVE.] Sb. Vys. Sk. Zemed. Brne A 17(1): 103-109. [In Czechoslovakian.] AA-486/71.

COLE CROPS ²³Brassica oleracea L., family Cruciferae
A large number of crops belongs to the plant species B. oleracea, known collectively as cole crops. Considerable difference of opinion exists among authorities as to the exact classification of these crops into subspecies, varieties, and subvarieties. Also, types will intercross, and the subsequent generation adds to the confusion. Nieuwhof (1969) separated the species into the following classification of varieties and subvarieties:

[gfx] fix info below into columns:

B. o., var. acephala DC. subvar. Iaciniata L. Curly Kale medullosa Thell. Marrow-stem kale millecapitata (Lev.) Thell. Thousand-head kale palmifolia DC. Tree kale plana Peterm. Smooth-leaf kale B. o., var. botrytis L. subvar. cauliflora DC. Cauliflower cymosa Lam. Sprouting (Italian) broccoli capitah L. f. alba DC. White cabbage f. rubra (L.) Thell. Red cabbage gemmifera DC. Brussels sprout gongylodes L. Kohlrabi sabauda L. Savoy cabbage

Nieuwhof (1969) considered collards and Portugal cabbage or tranchuda kales as transitional types between kales and cabbages.

In addition to the crops mentioned above, there are some other Brassicas for which little or no information exists on their pollination requirements. Because of the botanical relationship these requirements may be similar to known ones, although experience with some other crops has shown that even within a species the pollination requirements can be highly variable. These less well-known cruciferous crops grown primarily for their succulent leaves were listed by Bailey (1949*) as follows:

[gfx] fix info into columns:

B. carinata A. Br. Abyssinian mustard B. chinensis L. Pak-choi or Chinese cabbage B. fimbriata DC. Curled kitchen kale B. narinosa Bailey Broadbeaked mustard B. parachinensis Bailey Mock pak-choi B. pekinensis (Lour.) Rupr. Pe-tsai B. perviridis Bailey Tendergreen or spinach mustard B. ruvo Bailey Ruvo kale B. septiceps Bailey Seven-top or Italian kale

Cabbage and broccoli are the most important of the cole crops as indicated in table 10. Although cabbage is grown in more than half of the States on a total of 111,800 acres, Texas with 21,000; Florida with 17,600; New York with 11,200, and California with 9,700 acres account for more than half of the total production. The bulk of the broccoli, 30,600 acres of the 37,060 acres, and cauliflower, 17,900 of the 25,600 acres, produced in the United States came from California.

[gfx] fix table
TABLE 10.ÑAcreage and farm value of U.S. cole crops produced in 1970 __________________________________________________________ Crop Acreage harvested Dollar value (millions) __________________________________________________________ Broccoli, including sprouting broccoli 40,300 30 Brussels sprout 6,000 8 Cabbage 118,400 82 Cauliflower 23,900 22 Kale, including collards (1) (1) Kohlrabi (1) (1) __________________________________________________________ 1 Estimates discontinued.

__________
²³For some closely related crops, see "Mustard," p.261; "Radish," p. 314; "Rape," p. 315; and "Turnip and Rutabaga," p. 365.

Plant:
The cole crops are large-leaved, succulent, and low-growing, 1 to 2 feet, until the inflorescence is formed then they may reach 2 l/2 to 7 feet in height. More are biennial than annual, although most cauliflowers are annual. Nieuwhof (1969) stated that when annual varieties are crossed with biennial ones in temperate zones, the F_lis annual, but at slightly higher temperatures the F₁ might become biennial.

The plants are usually grown in cool climates or in the cooler part of the year in warm climates, and they do best under conditions of relatively high humidity. The leaves, buds, or sprouts are eaten either fresh (salad), cooked (usually blanched), or processed (sauerkraut) (figs. 82 - 84). The seed-stem is of value only in the production of seed. Unless seed is produced, the plant is destroyed or abandoned after the succulent portion is harvested.

There are many cultivars of the different subspecies or "varieties" of B. oleracea (Thompson 1964).

[gfx]
FIGURE 82. - Brussels sprouts plant, showing sprouts at proper harvesting stage.
FIGURE 83. - Broccoli plant with head at proper stage for harvesting.
FIGURE 84. - Kohlrabi plants properly spaced and almost large enough to harvest.

Inflorescence:
After leafy growth ceases, as for example the completed growth of the head of the cabbage, or the sprouts of Brussels sprouts, the flowering stem elongates. It is characterized by numerous branches (mostly from a main stem), small leaves, and numerous bright yellow or occasionally white flowers. The flowers of all Cruciferae have four petals, l/2 to 1 inch long, that appear to form a cross, hence the name Cruciferae (cross bearing).

The flower opens during the morning, the anthers a few hours later, so the flower is slightly protogynous. There are six stamens, two generally shorter than the style and facing toward it but leaning away, and four erect stamens generally longer than the style and also facing it. There is a single capitate stigma terminating the style (fig. 85). In most cultivars, nectar is secreted by two nectaries located between the bases of the short stamens and the ovary. Nieuwhof (1969) stated that there are also two inactive nectaries outside the base of the two pairs of long stamens. The nectaries secrete freely, 0.1 cm³ nectar each 24 hours of the 3 days the flower is open (Pearson 1933). The flowers are highly attractive to pollinating insects for both nectar and pollen. When the seed-producing acreage is large, beekeepers nearby frequently harvest a crop of excellent honey.

The blossom forms a silique, incorrectly but commonly called a pod, 1 to 4 inches long. A silique is distinguished by the unfolding of its two outer "shells," leaving the 10 to 30 seeds enfolded in a membranous partition. A well-fruited cabbage plant may produce one-half pound of seed (Pearson 1932); a Brussels sprouts plant, one-quarter pound (Sciaroni et al. 1953). Yields of 1,300 to 1,700 pounds of seeds per acre of cabbage can be expected, depending upon soil, climate, and cultural practices (Schudel 1952), although, as shown below, the average production of seed per acre is much below this amount. One acre should produce enough seed to plant several hundred acres. Nieuwhof (1969) recommended 1 to 5 kg seed per ha, roughly 1 to 5 lb/acre, the amount depending upon the preciseness of the planting method. If the seeds are planted in a bed, then the young plants transplanted to the field, only 80 to 200 g of seed per acre of plants are needed.

The acreage and production of Brassica seeds in the United States is shown in table 11.

[gfx] FIGURE 85. - Longitudinal section of collard flower, x 6.

Pollination Requirements:
The cole crops require cross-pollination. Only in some varieties of cauliflower is seed setting partly brought about by selfing (Nieuwhof 1963, 1969). In general, the flower is self-sterile (Detjen 1927, Kakizaki 1922). Many plants are self-incompatible, and some are cross- incompatible (Attia and Munger 1960, Detjen 1927, Garcia 1954, Odland and Noll 1950). The pollen must be effectively transferred between plants that are cross-compatible. Pearson (1930, 1932) concluded that Brassica plants were 95 percent cross-pollinated.

[gfx] fix table 11:

TABLE 11. - Acreage and production of Brassica seed crops in the United States _________________________________________________________ Harvested in- Production inÑ Kind of seed _____________________________________________ harvested 1969 1970 19711 1969 1970 19711 __________________________________ ____________________ Acres Thousand pounds Broccoli 51 97 120 56 78 85 Cabbage 358 526 664 200 351 402 Cauliflower 144 231 222 72 135 112 Kale 63 100 47 48 118 42 Kohlrabi 13 20 16 7 30 17 Mustard 379 193 204 444 288 220 Radish 1,880 1,348 1,347 1,641 1,389 1,157 Rutabaga 35 31 38 39 57 48 Turnip 591 481 422 856 758 482 __________________________________________________________ 1 Preliminary estimate

Moore and Anstey (1954) found up to 76 percent selfing in sprouting broccoli, but they did not indicate how much of the set was due to insect activity or if any of it resulted from the plants' own self-fertilization. Anstey (1954) found that 52 percent of sprouting broccoli plants were self-incompatible, 30 percent compatible, and 18 percent somewhere in between. But even with the compatible plants, the transfer of the pollen from anthers to stigma is necessary for best seed set.

Usually, plants grown in cages or otherwise isolated from pollinating agents set practically no seed even if the plants are occasionally shaken. Cross-pollinated cabbage flowers produced siliques with 10 or more seeds, but selfed flowers produced less than one seed each. Nieuwhof (1969) attributed this self-incompatibility to the fact that pollen on the stigma of the same plant germinates poorly, and he agreed with Knuth (1908*, pp. 74 - 128) that this incompatibility is strongest in freshly opened flowers. This illustrates Nature's abhorrence of selfing, accepting it reluctantly only as a last resort to preserve the species. The pollen must be transferred by an outside agent, and wind is not an important factor in its transfer, although Haskell (1943) and Jenkinson and Glynne-Jones (1953) stated that some pollen is moved by wind.

Many plants in the cole crops are male-sterile (East 1940, Nieuwhof 1961), and the use of this factor has been proposed in a hybrid seed production program (Attia and Munger 1950, Skrebtsova 1964). Sun (1937) showed that self-pollination of Brassica resulted in decreased yields in subsequent generations.

Increasing interest is developing in the production of hybrid seed. Legg and Souther (1968) showed that open-pollinated broccoli cultivars are unlikely to be used in a hybrid program, but Cole (1959) and Dickson (1970) reported finding a male-sterile mutant in sprouting broccoli, that might make hybrid seed production practical. Borchers (1968) showed that broccoli hybrids produced larger heads; 36 percent matured earlier and more uniformly than nonhybrids. Later, Borchers (1971) reported on the production of hybrid broccoli by using male-sterile plants with honey bees to do the crossing. Johnston (1964) demonstrated that hybrid vigor exists in the marrow-stem kale.

The most effective time for pollination during the 3 days the flower is open and the stigma is receptive has not been determined (Kakizaki 1925). More than one pollen-application period is probably necessary for fertilization of all the ovules in the ovary to produce a full silique.

Pollinators:
The construction of the flower is such that many kinds of insects can reach the pollen and nectar, including honey bees, wild bees, and flies. Blowflies have been used in cages where the pollination of only a few plants was involved (Faulkner 1962), but no practical method has been developed for their use in open-field pollination. Pearson (1932) considered bees of the family Andrenidae, Megachilidae, and Nomadidae [= Nomada spp. of Anthophoridae] more important than honey bees in the pollination of cabbage, but he did not say what the relative populations were, either on the plants or in the area. Sneep (1952) mentioned Bombus and Psithyrus but only incidentally.

Because cole crops flourish in cooler areas, the plants may come into bloom at temperatures below the minimum of about 55 degF at which honey bees fly. A few wild bees sometimes forage below this critical temperature, and if they are abundant, under such a climatic condition they could be important.

In general, the honey bee is the primary pollinator of cole crops (Hawthorn and Pollard 1964*, Jones and Rosa 1928 *, Nieuwhof 1969, United Nations 1961). It can be transported to the fields to be pollinated when desired. In the U.S.S.R., Skrebtsova (1964) reported that 84 to 94 percent of the pollinating agents on cabbage were honey bees. Radchenko (1966) reported that honey bees comprised 85 to 100 percent of the pollinators on cabbage, increased the seed crop by 300 percent over plants not freely visited, and that this visitation also considerably enhanced the seed quality. Sakharov (1958) showed that cabbage seeds from flowers receiving adequate bee visits were three times as large as those from flowers not visited by bees. Atkinson and Constable (1937) stated that the intense and repeated pollination that takes place within a cage when honey bees are enclosed results in more fruit set with more seeds per fruit than occurs in the open.

Pollination Recommendations and Practices:
Many publications on the production of cole crop seed give little or no consideration to the value of insect pollinators (Griffiths et al. 1946*), or these insects are considered only from the standpoint of varietal contamination (Baseman 1947 - 48, Knott 1949, Natl. Inst. Agr. Bot. 1942, Priestley 1954, Watts 1968).

The excellent United Nations (FAO) report (1961) stated that to insure good seed set of Brassicas, insect pollination of all the flowers is necessary. To accomplish this, they recommended placing colonies of bees near the larger fields but did not indicate how many colonies. Skirm (1971) said that bees were essential. Sakharov (1956) showed the following interesting relationship between a high density of bees and seed production and quality as follows:

[gfx] fix table:
__________________________________________________________ Method of pollination used ________________________________________ Saturated pollination Free Self Explanation by bees pollination pollination __________________________________________________________ Average seed yield per plant 46.6 0.9 0.1 Weight of 1,000 seed................grams 4.8 2.0 (1) Germination.......percent 96 64 0 __________________________________________________________ 1 "Puny."

Eckert (I959*), without supporting data, recommended two colonies per acre of all vegetable seed. Odland and Noll (1950) stated that a colony of bees located by their plots increased the seed yields. Oldham (1948) stated that having "a few colonies of bees dotted around the field" was a distinct advantage. When more than 5 or 10 acres are involved, the chances are good that the local supply of wild bees is inadequate for maximum flower visitation and seed set. If this is likely to be the case, the grower should arrange for the placement of strong colonies of honey bees in or adjacent to his field during flowering.

The number of colonies needed will doubtless vary with their strength, the size of the field, and the competing plants that might lure the bees from his field. Under some conditions, two coloniesÑas recommended by Eckert (1959*)Ñmight be adequate. Under other conditions where the grower is striving for maximum seed production, twice as many or more may be needed. In any case, where seeds of cole crops are produced commercially, the grower should take steps to assure the presence of the maximum population of insect pollinators.

LITERATURE CITED:
ANSTEY, T. H.
1954. SELF-INCOMPATIBILITY IN GREEN SPROUTING BROCCOLI (BRASSICA OLERACEA L., VAR. ITALICA PLENCK) 1. ITS OCCURRENCE AND POSSIBLE USE IN A BREEDING PROGRAM. Canad. Jour. Agr. Sci. 34: 59-64.

ATKINSON W. T., and CONSTABLE, E. E.
1937 A HONEY BEE TECHNIQUE IN SEED PRODUCTION OF SELECTED CRUCIFEROUS PLANTS. Australasian Beekeeper 39(6): 183-185.

ATTIA M. S., and MONGER, H. M.
1950. SELF-INCOMPATIBILITY AND THE PRODUCTION OF HYBRID CABBAGE SEED. Amer. Soc. Hort. Sci. Proc. 56: 363 - 368.

BATEMAN A. J.
1947-48. CONTAMINATION OF SEED CROPS: 1. INSECT POLLINATION. Jour. Genet. 48: 257-275.

BORCHERS E. A.
1968 YIELD, UNIFORMITY OF HEADING AND SEASON OF MATURITY OF BROCCOLI INBREDS, HYBRIDS AND VARIETIES. Amer. Soc. Hort. Sci. Proc. 93: 352 - 355.

BORCHERS, E. A.
1971. HYBRID BROCCOLI SEED PRODUCTION UTILIZING THE M6 GENE FOR MALE STERILITY. Amer. Soc. Hort. Sci. Proc. 96: 542-543.

COLE, K.
1959. INHERITANCE OF MALE-STERILITY IN GREEN SPROUTING BROCCOLI. Canad. Jour. Genet. Cytol. 1: 203-207.

DETJEN, L. R.
1927. STERILITY IN THE COMMON CABBAGE (BRASSICA OLERACEA L.). Hort. Soc. N.Y. Mem. 3: 277-280.

DICKSON. M. H.
1970. A TEMPERATURE SENSITIVE MALE STERILE GENE IN BROCCOLI BRASSICA OLERACEA L., VAR. ITALICA. Amer. Soc. Hort. Sci. Proc. 95(1): 13-14

EAST, E. M.
1940. THE DISTRIBUTION OF SELF-STERILITY IN THE FLOWERING PLANTS. Amer. Phil. Soc. Proc. 82: 449-518.

FAULKNER, G. J.
1962. BLOWFLIES AS POLLINATORS OF BRASSICA CROPS. Com. Grower [England] 3457: 807-809.

GARCIA, G. M.
1954. A PRELIMINARY STUDY OF THE PRODUCTION OF CAULIFLOWER SEED. Philippine Jour. Agr. 19: 143-152.

HASKELL, G.
1943. SPATIAL ISOLATION OF SEED CROPS. Nature 152: 591-592.

JENKINSON, J. G., and GLYNNE-JONES, G. D.
1953. OBSERVATIONS ON THE POLLINATION OF OIL RAPE AND BROCCOLI. Bee World 34: 173 - 177.

JOHNSTON, T. D.
1964. INBREEDING AND HYBRID PRODUCTION IN MARROW-STEM KALE (BRASSICA OLERACEA L., VAR. ACEPHALA D.D.). Euphytica 13: 147-152.

KAKIZAKI, Y.
1922. SELF-STERILITY IN CHINESE CABBAGE. Jour. Hered. 13: 374 - 376.

______ 1925. A PRELIMINARY REPORT OF CROSSING EXPERIMENTS WITH CRUCIFEROUS PLANTS WITH SPECIAL REFERENCE TO SEXUAL COMPATIBILITY AND MATROCLINOUS HYBRIDS. Jap. Jour. Genet. 3(2): 49-77.

KNOTT, J. E.
1949. VEGETABLE GROWING. Ed. 4, 314 pp. Lea and Eebiger, Philadelphia.

LEGG, P. D., and SOOTHER, E. D.
1968. HETEROSIS IN INTERVARIETAL CROSSES IN BROCCOLI (BRASSICA OLERACEA VAR. ITALICA). Amer. Soc. Hort. Sci. Proc. 92: 432-437.

MOORE, J. F., and ANSTEY, T. H.
1954. A STUDY OF THE DEGREE OF NATURAL SELFING IN GREEN SPROUTING BROCCOLI (BRASSICA OLERACEAE L., VAR. ITALICA PLENCK) A NORMALLY CROSS-POLLINATED CROP. Amer. Soc. Hort. Sci. Proc. 63: 440 - 442.

NATIONAL INSTITUTE OF AGRICULTURAL BOTANY [ENGLAND].
1942. CROSS-FERTILIZATION IN BRASSICAS. Min. Agr. Jour. 49(2): 116-117.

NIEUWHOF, M.
1961. MALE STERILITY IN SOME COLE CROPS. Euphytica 10: 351-356.

NIEUWHOF, M.
1963. POLLINATION AND CONTAMINATION OF BRASSICA OLERACEA L. Euphytica 12: 17-26.

______ 1969. COLE CROPS. 353 pp. Leonard Hill, London.

ODLAND, M. L., and NOLL, C. J.
1950. THE UTILIZATION OF CROSS COMPATIBILITY AND SELF- INCOMPATIBILITY IN THE PRODUCTION OF F₁ HYBRID CABBAGE. Amer. Hort. Sci. Soc. Proc. 55, 391-402.

OLDHAM, C. H.
1948. BRASSICA CROPS AND ALLIED CRUCIFEROUS CROPS. 295 pp. Lockwood, London.

PEARSON, O. H.
1930. OBSERVATIONS ON THE TYPE OF STERILITY IN BRASSICA OLERACEA VAR. CAPITATA. Amer. Soc. Hort. Sci. Proc. 34 - 38.

______ 1932. BREEDING PLANTS OF THE CABBAGE GROUP. Calif. Agr. Expt. Sta. Bul. 532, 22 pp.

______ 1933. STUDY OF THE LIFE HISTORY OF BRASSICA OLERACEA. Bot. Gaz. 94: 534-550.

PRIESTLEY G.
1954. USE OF HONEY BEES AS POLLINATORS IN UNHEATED GLASSHOUSES. New Zeal. Jour. Sci. and Technol. 36(3): 232 - 236.

RADCHENKO, T. H.
1966. [ROLE OF HONEY BEES AS POLLINATORS IN INCREASING THE SEED CROP FROM CABBAGE AND RADISH.] Bdzhil'nytstvo 2: 72-74. [In Ukrainian.] AA-390/69.

SAKHAROV, M. K.
1956. [CABBAGE POLLINATION BY BEES.] In Krishchunas, I. V., and Gubin, A. F., eds. [Pollination of Agricultural Plants], pp. 180-181, Moskva, Gos. lzd-vo Sel-khoz. Lit-ry. [In Russian.]

SAKHAROV M. K.
1958. [POLLINATING ACTIVITY OF BEES ON SEED-BEARING PLANTS IN VEGETABLE CULTIVATION. ] Sad i Ogorod 96(7): 21 - 23. [In Russian.]

SCHUDEL, H. L.
1952. VEGETABLE SEED PRODUCTION IN OREGON. Oreg. Agr. Expt. Sta. Bul. 512, 79 pp.

SCIARONI, R. H., LANGE, W. H., JR., MINGES, P. A., and SNYDER, W. C.
1953. BRUSSEL SPROUTS PRODUCTION IN CALIFORNIA. Calif. Agr. Expt. Sta. Cir. 427, 16 pp.

SKIRM, G. W.
1971. [HYBRID CABBAGE.] Industrielle Obst- und Gemuseverwertung 56(5): 120 - 121. [In German, English abstract.]

SKREBSOVA, N.D.
1964. [USE OF THE POLLINATING ACTIVITY OF HONEYBEES FOR PRODUCING HYBRID VEGETABLE SEED. ] Trud. Nauch. -Issled. lnst. Pchelovod.: 223-245. [In Russian, English summary.]

SNEEP, J
1952. SELECTION AND BREEDING OF SOME BRASSICA PLANTS. Internatl. Hort. Cong. Rpt. 13: 422 - 426.

SUN, C. VON.
1937. EFFECTS OF SELF-POLLINATION IN RAPE. Jour. Amer. Soc. Agron. 29: 555 - 567.

THOMPSON, R. C.
1954. CAULIFLOWER AND BROCCOLI; VARIETIES AND CULTURE. U.S. Dept. Agr. Farmers' Bul. 1957, 16 pp.

UNITED NATIONS FOOD AND AGRICULTURE ORGANIZATION ( FAO)
1961. AGRICULTURAL AND HORTICULTURAL SEEDS. FAO Agro-studies 55, 531 pp.

WATTS, L. E.
1968. NATURAL CROSS-POLLINATION AND THE IDENTIFICATION OF HYBRIDS BETWEEN BOTANICAL VARIETIES OF BRASSICA OLERACEA L. Euphytica 17: 74-80.

CORIANDER
Coriandrum sativum L., family Umbelliferae
Coriander is a minor crop grown for its aromatic seeds and oil, which are used in the flavoring of food, in certain drinks and in medicine. It is extensively cultivated in India and grown to some extent in Europe and Brazil, with only a few acres in the United States.

Plant:
The plant is a strong-smelling annual, 1 to 3 feet high, and is cultivated somewhat like carrots. Yields of 2,000 to 3,000 pounds of dried seed per acre are obtained in India (Purseglove 1968*).

Inflorescence:
The coriander flower has five irregular-shaped petals, five stamens, five sepals, and two styles. The white to pinkish flowers are in umbels. The first umbels to bloom have hermaphrodite flowers, with possibly a few staminate ones (fig. 86). The later umbels have only staminate flowers. The hermaphrodite flowers are completely protandrous, so that selfing is impossible. After the pollen is gone, the stigmas become receptive and are liable to crossing with other plants; however, the umbels of staminate flowers may develop in such a way that they are right over the receptive stigmas of later flowers. When these anthers dehisce, the pollen is thrown out and falls to the stigmas below in crumbling masses. In this way, some of the stigmas may be pollinated even if an insect has not brought pollen from another flower (Kerner 1897* p. 325).

Pollen is produced in the pinkish anthers. Nectar is freely secreted on the ovary. The blossoms are highly attractive to both pollen-collecting and nectar-collecting insects (Glukhov 1956), and honey bees "go a bit frantic" over them (Pellett 1947*).

[gfx]
FIGURE 86. - Longitudinal section of coriander flower, x 40. A, Staminate stage; B, pistillate stage.

Pollination Requirements:
Although the coriander plant is partially self-fertile, bees are beneficial to it. Glukhov (1955, p. 216) reported that when they were excluded only 49.4 percent of the seeds set, but when they were present 68.3 percent of the seeds set. With the possible yield of 2,000 to 3,000 lb/acre, the above bee effect would be of significance. Bogoyavlenskii and Akimenko (1966) associated seed yields with greater insect visitation.

Pollinators:
Honey bees are apparently ideal pollinators of Coriander.

Pollination Recommendations and Practices:
None.

LITERATURE CITED:
BOGOYAVLENSEII, S. H., and AKIMENKO, A. L.
1966. [ CORIANDER AS A NECTIFEROUS AND ENTOMOPHILLOUS CULTURE.] In Achievements of Science and Advanced Experiment in Beekeeping, pp. 119-125. Papers presented at the All-Russian conference of Apicultural Researchers, Dec. 21-23, 1965, Moscow. [In Russian. ] AA-141/70.

GLUKHOV M. M.
1955. [HONEY PLANTS.] 512 pp. Izd. 6, Perer. i Dop. Moskva, Gos. Izd-vo Selkhoz Lit-ry. [In Russian.]

CUCUMBER AND GHERKIN
Cucumis sativus L., family Cucurbitaceae
Cucumbers and gherkins are grown in most of the States to some extent but over half of the 179,400 acres devoted to this crop in 1969 was in five States: North Carolina (34,100), Michigan (23,100), Wisconsin (13,900), Florida (16,400), and Texas (10,900). The 1969 crop was valued at $78 million, of which $32 million was derived from cucumbers marketed in the fresh state and $46 million from processed cucumbers.

The so-called gherkin of American commerce is a small-fruited cucumber type processed in a special way. The true gherkin, or West Indian gherkin, is another species (C. anguria L.). It is grown primarily in Brazil and occasionally in the West Indies. Its fruit is somewhat oval rather than oblong like the cucumber (Purseglove 1968 *).

Plant:
The cucumber is a trailing or climbing, normally monoecious, annual herb, with vines 2 to 10 feet long covered with stiff bristly hairs. The roughly triangular leaves are 3 to 10 inches across, and they are supported on 3- to 7-inch petioles or stems, which permit the leaves to overshadow the prostrate branches, flowers, and fruit (Whitaker and Davis 1962*).

Chao-Shan and Humphries (1969) studied fruit setting on the vines of three cultivars in North Carolina, and found that 75 to 90 percent of the fruit set within 20 inches, and the bulk with 12 inches, of the crown.

Two main types of fruit are grown commercially in the United States - the slicing- or salad-type cucumber and the pickling cucumber. The two types have been developed for their specific uses and differ in production methods.

The fruit is pendulous and oblong and has a relatively large stem. Particularly when young, its skin has spiny, wortlike tubercles. It has a characteristic odor and taste that make it not too palatable alone, but delicious in salads. The majority of the fruit is consumed as processed pickles.

The plant requires warm weather but not as hot as that required by watermelons. Some crops of salad-type cucumbers are grown under glass in cold countries to supply off-season demands for the fresh fruits. Greenhouse cucumbers are usually more uniform than fieldgrown ones, primarily because of better control of plant growth and environmental conditions including insect pollination. An estimated 20 percent of the pickling cucumbers were machine harvested in 1967, and the percentage is increasing (Zahara and Sims 1966, Sims and Zahara 1968).

In Europe, and to some extent in the United States, a special slicing cucumber sets fruit parthenocarpically (without pollination) (Strong 1931, Whitaker and Jagger 1937). It sets no seed unless pollinated. If seeds are produced they detract from its eating quality (Kettner 1967). In some areas in Europe where this cucumber is grown, beekeepers are required to remove their bees from the area during the flowering period (Milne 1941, van Berkel 1960, van Berkel and Vriend 1957, van Koot 1960). In such areas, the planting of phacelia is recommended so that it flowers simultaneously with this cucumber and lures the bees from the cucumber flowers (Proefstation Voor de Groentenen Fruitteelt onder Glaste Naaldwijk 1958).

Inflorescence:
Cucumber flowers are axillate and quite similar to those of muskmelons. The staminate ones are borne in clusters, each flower on a slender peduncle or stem. The pistillate ones are usually borne solitary on a stout peduncle. As in other cucurbits, the pistillate flower is easily recognized by the large ovary at the base of the flower. In the muskmelon, the ovary is covered with soft hairs, but in the cucumber it is sparsely covered with spiny wortlike growths. The yellow, wrinkled petals are similar in size and shape to those of the muskmelon. The pistillate flower has three thick stigma lobes atop a short broad style (Heimlich 1927). Normal cucumber types have staminate and pistillate flowers in varying proportions depending on plant growth, vigor, and environmental conditions.

The staminate flowers (fig. 103) usually appear about 10 days before the first pistillate flowers appear (Judson 1929). They normally out-number the pistillate flowers about 10 to 1 (Alex 1957), but this ratio has been known to reach 100 to 1, and there are seasonal variations in the ratio (Currence 1932, Edmond 1931). This ratio can be altered also by the application of certain pheromone chemicals (McMurray and Miller 1968, Robinson et al. 1968, Sims and Gledhill 1969).

In the recently developed "gynoecious" plants, the flowers are predominantly pistillate (Peterson 1960, Peterson and Anhder 1960, Peterson and de Zeeux 1963, Peterson and Weigle 1958).

Pollination Requirements:
The need for insect pollination of cucumbers has been known for years. Before the turn of the century, honey bees were used to pollinate cucumbers grown under glass (McIntosh 1855, Root 1886, Pieters 1896, Hunn and Craig 1905, Corbett 1906, Lyon 1906). Later tests experimentally confirmed this need (Markov and Romanchuk 1959). The need for bees on fieldgrown cucumbers was also recognized (Jones and Rosa 1928*), and growers in localities where bees were scarce were advised to keep honey bees to insure fruit set (Beattie 1928, Seaton et al. 1936). More recent tests have verified earlier ones (Alex 1959, Beattie 1935, Connor and Martin 1 969a, b, 1970, Martin and Collison).²⁸ Edgecombe (1946a, b) also reported that he used bees in the field for the transfer of pollen between cultivars for the production of hybrid cucumber seed. Numerous tests have shown that all present varieties of cucumber are inter-fertile, but the pollen must be transferred to the stigma by a pollinating agent, usually honey bees.

The exception is the previously mentioned parthenocarpic slicing cultivars. McCollum (1934) showed that the setting of fruit on these cultivars does not produce the inhibiting effect on plant growth comparable to that caused by fertilized fruit.

The relative time of anthesis in staminate and pistillate cucumber flower was determined by Atsmon et al. (1965). Connor (1969) found that the best time of day for effective cucumber pollination in Michigan was from 10 a.m. to 3 p.m. He also found that pollination was about equally effective whether the pollen was placed on one lobe of the stigma or on all the lobes. Seaton et al. (1936) also stated the stigma is receptive throughout the day but most receptive in the early morning and that several hundred pollen grains should reach the stigma for most effective pollination.

The pollination requirements of pickling cucumbers vary greatly with the variety used, the method of production, and the geographic area. Traditionally, pickling cucumbers have been produced on monoecious vines, planted at the rate of about 5,000 to 15,000 plants per acre. The first one or two fruits on each vine are handpicked when they reach the desired size, usually a few days after flowering. The vine continues to grow and set fruit, which is harvested in a succession of handpickings throughout the season, but the trend is toward machine harvesting (Stout et al. 1964).

During the 1960's the introduction of gynoecious cucumbers and the development of harvesting machines launched a new era in pickle production. The machine usually destroys the plant a's it harvests the fruit so there is only one harvest, commonly called a destructive harvest of the crop, although nondestructive or "multiple-pick" harvesting machines are also available. Yield somewhat comparable to a succession of handpickings is obtainable by planting 50,000 to 150,000 (that is, about 10 times as many) plants per acre and carrying out one machine harvest averaging one or two cucumbers per vine.

The gynoecious characteristic was an innovation designed to provide pistillate flowers in rapid succession. Staminate flowers are provided by blending in about 10 percent seed of a monoecious type. With adequate pollination, fruit forms quickly and, under favorable weather conditions, grows uniformly to an optimum size for machine harvesting. These revolutionary changes in pickling cucumber production have greatly increased the need for timely and adequate pollination because of the greater concentration of pistillate flowers and the need for more rapid, uniform fruit set necessary for a single machine harvest.

Pollinators:
Although cucumber flowers are attractive to bees, the crop is not considered a major source of nectar or pollen. Individual flowers produce relatively large amounts of nectar, but the number of flowers per acre is low relative to that of our major honey plants. Pellett (1947*) stated that in numerous localities cucumbers are of some importance to bees. Stephen (1970a) stated that bees get little pollen from cucumbers, and that pistillate and staminate flowers are about equally attractive.

Connor (1969) and Martin (1970) stated that even when honey bees visit staminate flowers, the primary objective is to collect nectar, and that cucumbers are visited for pollen largely when other sources of pollen are absent. Shemetkov (1960b) in Russia and Amaral et al. (1963) in Brazil reported that bees collected cucumber pollen heavily from 8 to 10 a.m. and nectar from 10 a.m. to noon. Bees work the blossoms later in the day in springtime or cooler climates than in summer or warmer climates. Nemirovich-Danchenko (1964) reported that nectar secretion was greatest 3 to 4 hours after the flower opens. Skrebtsova (1960) stated that pistillate flowers produce more nectar sugar than staminate ones. Amaral et al. (1963) concluded that bees show no preference for staminate over pistillate flowers. Connor and Martin (1969a, b) stated that in Michigan "native bees cannot and should not be relied upon as pollinators. The honey bee is the primary and only dependable pollinator of cucumbers." Tsyganov (1953) considered one bee equal in value to 11,000 thrips as pollinators of cocumbers. Skrebtsova (1964) stated that honey bees represented 84 to 96 percent of the insect pollinators on cucumbers. In many U.S. fields, they are the only pollinators present. Szabo and Smith (1970) reported that the leafcutter bee, Megachile pacifica, worked cucumbers in a greenhouse if the temperature remained at 30 deg C. Stephen (1970b) reported that honey bees failed to work effectively in plastic greenhouses, apparently because of the reduction in ultraviolet light.

Shemetkov (1957, 1960a) showed that a cucumber flower should be visited 8 to 10 times for satisfactory fruit set, but the number of seeds and weight of fruit increases up to 40 to 50 visits. Connor (1969) also found that as many as eight visits per flower were necessary for maximum set, and seed production was significantly greater with 20 or more visits than with 10 visits. Anderson (1941) stated that "nubbins," "balls," and "crooks" were the result of poor pollination resulting from too few bee visits per flower. Seaton (1937) reported that uniform fruits weighed 626 g and had 314 seeds, but constricted fruits weighed only half as much and had only 150 seeds.

Knysh (1958) removed and tested the viability of pollen from bees flying 250, 500, 750, and 1,000 m to the hive. He found that 38 percent of pollen grains taken from bees flying 250 m were viable but only 18 percent from bees flying 500 m. He found no viability in pollen grains that were carried greater distances. This indicates that the pollen grains exposed on the bee have a relatively short lifespan. Seyman et al. (1969) reported the importance of honey bees in cucumber production by obtaining increased fruit yield with increased exposure to bee activity. Shemetkov (1960a) calculated that one colony of bees was equal to 300 man-days in pollination of cucumbers.

In Michigan, one colony to 2 or 3 acres have been used to pollinate monoecious type cucumbers for handpicking. The flowers are attractive to bees, and even though the number of flowers per acre is low, bees continue to visit and pollinate the blossoms as they mature. The gynoecious hybrids grown for machine harvest present a different picture. Here the current Michigan recommendation is one colony to each 50,000 plants, or one to three colonies per acre (Martin 1970).

Connor and Martin (1970) using highly gynoecious cultivars showed that preventing the pollination of cucumber flowers for periods up to 11 days after the appearance of the first pistillate flowers resulted in higher yields of more uniform pickles. Unfortunately, this cannot yet be duplicated on a field basis because commercially developed gynoecious hybrids have not so far been able to maintain the gynoecious characteristic at a sufficiently high level to delay pollination. That is, present gynoecious hybrids produce some staminate flowers, so pollen is available as soon as pistillate flowers are produced. If fully gynoecious hybrids become available, growers may interplant a few rows of monoecious plants with gynoecious hybrids in such a way that staminate flowers appear later than pistillate flowers. Pollination could thus be delayed until the gynoecious plants attained better growth and capacity to produce a higher yield of more desirably shaped fruit. This points out that pollination studies coordinated with studies of other cultural practices including plant breeding may have broader application than has been fully appreciated to date.

Pollination Recommendations and Practices:
The literature leaves little doubt that insect pollination of cucumbers in the United States is essential to profitable production, and that honey bees are the primary pollinating agents. The question of the number of pollinators per unit area (acres or flowers) is not completely resolved. Recommendations have varied from "fields no farther than one- fourth mile from one or more swarms," to "a few stands [colonies] in or near the field," or from one colony per 10 acres to one strong colony per acre (Anonymous 1959; Alex 1959; Conner 1969; Conner and Martin 1969a, b; Davis and Hall 1958; Eckert 1959*; Martin 1970; Peto 1951; Seyman et al. 1969; Sims and Zahara 1968; Steinhauer 1970, 1971; Warren 1961, 1967). Hughes (1971) recommended 30 to 40 bees within a 30-foot circle. The University of Arizona (1970) recommended one bee per 100 flowers.

Recommendations should differ between monoecious, handpicked, low plant population, and gynoecious, single-machine-harvest, high plant population. Many of the recommendations that have been made are mere statements without supporting data, and, as might be expected, they vary considerably. The most thorough study of cucumber pollination has been made in Michigan (Connor 1969, Connor and Martin 1969a 1970, Martin and Collison 1970). It is of interest to note that although one strong colony per acre is recommended (Connor 1969, Connor and Martin 1969a, b) or "one colony per acre 2 or 3 might pay off" (Martin and Collison 1970), the data by Connor and Martin (1970) leave little doubt that production with three colonies per acre was significantly below their bee saturation (cage) population. In Michigan, more than three colonies per acre were required for maximum cucumber production when gynoecious hybrids were grown for machine harvest. Davis et al. (1970) indicated that honey bees were more effective if they were moved to the cucumber field after flowering had started. This was supported by Martin (1970) who showed that delayed pollination improved yield and fruit shape. Enzie (1934) stated that when bees are scarce it may be necessary to distribute hives among the larger plantings.

Hughes (1971) gave the most practical recommendation. He stated that, on a clear day walk into the cucumber field. If you cannot count 30 to 40 bees in a 30-foot diameter (within 15 feet) or cannot hear a very noticeable hum you probably need to bring in more bees. He generally recommended one colony per acre as essential, with two or more as desirable, or one bee per 100 flowers.

LITERATURE CITED:
ANONYMOUS.
1959. PRODUCTION AND PRODUCTION REQUIREMENTS OF CROPSÑHIGH PLAINS. Tex. Agr. Expt. Sta. Misc. Pub. 330, 21 pp.

ALEX, A. H.
1957. HONEYBEES AID POLLINATION OF CUCUMBERS AND CANTALOUPES. Tex. Agr. Expt. Sta. Prog. Rpt. 1936, 4 pp.

____ 1959. HONEYBEES FOR POLLINATING CUCURBIT CROPS. Tex. Briefs 2(4): 18 - 20.

AMARAL. E., MITIDIERI, J., and VENCOUSKY, R.
1963. [STUDIES ON THE ACTIVITIES OF APIS MELLIFERA L. WHILE VISITING THE FLOWERS OF CUCUMIS SATIVUS L.] Olericultura [Brazil] 3: 181 - 193. [In Portuguese, English summary.]

ANDERSON, W. S.
1941. GROWING CUCUMBERS FOR PICKLING IN MISSISSIPPI. Miss. Agr. Expt. Sta. Bul. 355, 17 pp.

ATSMON, D., GALUN, E., and JAKOB, K. B.
1965. RELATIVE TIME OF ANTHESIS IN PISTILLATE AND STAMINATE CUCUMBER FLOWERS. Ann. Bot. 29: 277 - 283.

BEATTIE, J. H.
1935. THE PRODUCTION OF CUCUMBERS IN GREENHOUSES. U.S. Dept. Agr. Farmers' Bul. 1320, rev., 30 pp.

BEATTIE, W. R.
1928. CUCUMBER GROWING. U.S. Dept. Agr. Farmers' Bul. 1563, 22 pp.

BERKEL, N. VAN.
1960. [SEED-HEADS IN CUCUMBERS.] Jversl. Proefst. Groenten Fruitt. Naaldwijk 1959: 122 - 123. [In Dutch, English summary.] AA-949l63.

____ and VRIEND. S.
1957. [SEED-HEADS IN CUCUMBERS.] Jversl. Proefst. Groenten Fruitt. Naaldwijk 1956: 117 - 120. [In Dutch.] AA-948/63.

CHAO-SHAN SU and HUMPHRIES E. G.
1969. FRUIT-SET PATTERNS OF PICKLING CUCUMBERS. Amer. Soc. Agr. Engin. Trans. 12: 522 - 523.

CONNOR, L. J.
1969. HONEY BEE POLLINATION REQUIREMENTS OF HYBRID CUCUMBERS CUCUMIS SATIVUS L. 150 pp. M.A. Thesis, Mich. State Univ.

_____and MARTIN, E. C.
1969a. HONEY BEE POLLINATION OF CUCUMBERS. Amer. Bee Jour. 109: 389.

CONNOR, L. J., and MARTIN, E. C.
1969b. HONEY BEE POLLINATION OF CUCUMBERS. Pickle Pak 29: 3.

____ and MARTIN, E. C.
1970. THE EFFECT OF DELAYED POLLINATION ON YIELD OF CUCUMBERS GROWN FOR MACHINE HARVEST. Amer. Soc. Hort. Sci. Proc. 95: 456 - 458.

CORBETT, L. C.
1906. CUCUMBERS. U.S. Dept. Agr. Farmers' Bul. 254, 30 pp.

CURRENCE, T. M.
1932. NODAL SEQUENCE OF FLOWER TYPE IN THE CUCUMBER. Amer. Soc. Hort. Sci. Proc. 29: 477 - 479.

DAVIS, G. N., and HALL, B. J.
1958. CUCUMBER PRODUCTION IN CALIFORNIA. Calif. Agr. Expt. Sta. and Ext. Serv. Manual 24, 21 pp.

DAVIS, L. B., LASTER, M. L., and CAMPBELL, G. M.
1970. STUDY SHOWS NEW BEES BETTER FOR CUCUMBER FIELDS. Miss. Farm Res. 33(6): 1, 2.

EDGECOMBE, S. W.
1946a. HONEYBEES AS POLLINATORS IN THE PRODUCTION OF HYBRID CUCUMBER SEED. In lowa State Apiarist Rpt. 1945, pp. 85-86.

____ 1946b. HONEYBEES AS POLLINATORS IN THE PRODUCTION OF HYBRID CUCUMBER SEED. Amer. Bee Jour. 86: 147.

EDMOND, J. B.
1931. SEASONAL VARIATION IN SEX EXPRESSION OF CERTAIN CUCUMBER VARIETIES. Amer. Soc. Hort. Sci. Proc. 27: 329 - 332.

ENZIE, W. D.
1934. CUCUMBER GROWING IN NEW YORK. N.Y. Agr. Expt. Sta. Cir. 150, 7 pp.

HEIMLICH L. F.
1921. THE DEVELOPMENT AND ANATOMY OF THE STAMINATE FLOWER OF THE CUCUMBER. Amer. Jour. Bot. 14: 227-237.

HUGHES, G. R.
1971. IN PICKLING CUCUMBERS - BEES MAKE THE DIFFERENCE. Prog. Farmer 86(6): 16 - 17.

HUNN, C. E., and CRAIG, J.
1905. 1. SECOND REPORT ON THE FORCING OF STRAWBERRIES. 2. NOTES ON THE FORCING OF TOMATOES, CUCUMBERS AND MELONS. N.Y. (Cornell) Agr. Expt. Sta. Bul. 231: 239-271.

JUDSON, J. E.
1929. THE MORPHOLOGY AND VASCULAR ANATOMY OF THE PISTILLATE FLOWER OF THE CUCUMBER. Amer. Jour. Bot. 16: 69 - 89.

KETTNER H.
1967. [EXPERIMENT WITH HONEYBEES FOR POLLINATING CUCUMBERS IN GREENHOUSES.] Garten u. Kleintierz 6(17): 12-13. [In Germam] AA-791/71.

KNYSH, A. N.
1958. [POLLINATION BY BEES OF VARIETIES OF CUCUMBER.] Sad i Ogorod 6: 13 - 16. [In Russian.] AA-372/58.

KOOT I. J. VAN.
1960. [THE INFLUENCE OF BEES ON BULL-NECKED CUCUMBERS.] Netherlands, Directeur van de Tuinbouw Meded. 23: 735-764. [In Dutch, English summary.]

LYON D.
1906. HONEY-BEES AND CUCUMBERS. Gleanings Bee Cult. 34: 509-511.

MARKOV, I., and ROMANCHUK I.
1959. [POLLINATION OF CUCUMBERS BY HONEYBEES.] Sel'sk. Khoz. Sibiri 2: 53 - 54. [ In Russian. ] AA-237/61.

MARTIN, E. C.
1970. THE USE OF HONEY BEES IN THE PRODUCTION OF HYBRID CUCUMBERS FOR MECHANICAL HARVEST. In The Indispensable Pollinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp. 106 - 109.

MCCOLLUM, J. P.
1934. VEGETATIVE AND REPRODUCTIVE RESPONSES ASSOCIATED WITH FRUIT DEVELOPMENT IN THE CUCUMBER. N.Y. (Cornell) Agr. Expt. Sta. Mem. 163: 1 - 27.

McINTOSH, C.
1855. THE CUCUMBER AND MELON. In Book of the Garden, pp. 662-668. Edinburgh and London. 2 vol.

McMURRAY, A. L., and MILLER, C. H.
1968. CUCUMBER SEX EXPRESSION MODIFIED BY 2- CHLOROETHANEPHOSPHONIC ACID. Science 162: 1397 - 1398.

McMURRAY, A. L., AND MILLER, C. H.
1941. POLLINATION OF CUCUMBERS BY BEES. Brit. Bee Jour. 66(3099): 353.

NEMIROVICH-DANCHENKO, E. N.
1964. [CONCERNING THE NECTAR YIELD AND FLORAL BIOLOGY OF CUCUMBERS.] Izv. Tomsk. Otd. Vses. Bot. Obshch. 5: 127-132. [In Russian.] AA-541/67.

PETERSON, C. E.
1960. A GYNOECIOUS INBRED LINE OF CUCUMBER. Mich. Agr. Expt. Sta. Quart. Bul. 43: 40 - 42.

____ and ANHDER, L. D. 1960. INDUCTION OF STAMINATE FLOWERS ON GYNOECIOUS CUCUMBERS WITH GIBBERELLIN A3. Science 131: 1673 - 1674.

____ and ZEEUX, D. J. DE.
1963. THE HYBRID PICKLING CUCUMBER, 'SPARTAN DAWN'. Mich. Agr. Expt. Sta. Quart. Bul. 46: 267 - 273.

____ and WEIGLE, J. L.
1958. A NEW METHOD FOR PRODUCING HYBRID CUCUMBER SEED. Mich Agr. Expt. Sta. Quart. Bul. 40: 960-965.

PETO, H. B.
1951. POLLINATION OF CUCUMBERS, WATERMELONS AND CANTALOUPES. In Iowa State Apiarist Rpt. 1950, pp. 79-87.

PIETERS, A. J.
1896. SEED PRODUCTION AND SEED SAVING. U.S. Dept. Agr. Yearbook 1896: 207-216.

PROEFSTATION VOOR DE GROENTENEN FRUITTEELT ONDER GLASTE NAALDWIJK.
1958. [SEED-HEADS IN CUCUMBERS.] Jversl. Proefst. Groenten Fruitt. Naaldwijk: 132 121 (1959); 128 (1960); 129 (1961), 170 (1962j. [ In Dutch ] AA-950/ 63.

ROBINSON, R. W., SHANNON, S., and GUARDIA, M. DE LA.
1968. REGULATION OF SEX EXPRESSION IN THE CUCUMBER. Bioscience 19: 141 -142.

ROOT, A. I.
1886. RAISING CUCUMBERS IN GREENHOUSES, FOR THE BOSTON MARKET. Gleanings Bee Cult. 14: 735-737. 208

SEATON, H. L.
1937. RELATION OF NUMBER OF SEEDS TO FRUIT SIZE AND SHAPE IN CUCUMBER. Amer. Soc. Hort. Sci. Proc. 35: 654-658.

____ HUTSON, R., and MUNCIE, J. H.
1936. THE PRODUCTION OF CUCUMBERS FOR PICKLING PURPOSES. Mich. Agr. Expt. Sta. Spec. Bul. 273, 131 pp.

SEYMAN, W. S., BARNETT, W. W., THORP, R. W., and others.
1969. BEE POLLINATION IN CUCUMBERS FOR PICKLING. Calif. Agr. 23(1): 12 - 14.

SHEMETKOV, M. F.
1957. [THE USE OF BEES FOR POLLINATING CUCUMBERS IN HOT HOUSES AND FORCING BEDS.] Biul. Nauch.Tekh. Inf. Inst. Pchelovod. 2: 21 - 24. [In Russian.]

____1960a. [PARTICULARITIES AS TO THE UTILIZATION OF BEES FOR POLLINATION PURPOSES OF CUCUMBER CULTURES IN GREENHOUSES AND HOTBEDS.] In Nauchno-Issled. Inst. Pchelovod. Nauchnolssled. Inst. Ovoshchnogo Khoz., pp. 49-58. [In Russian.]

____ 1960b. [(CUCUMBER) POLLINATING ACTIVITY OF BEES IN GREENHOUSES.] Pchelovodstvo 37(1): 28-31. [ In Russian. ] AA-437/63.

SIMS, W. L., and GLEDHILL, B. L.
1969. ETHREL EFFECTS ON SEX EXPRESSION, AND GROWTH DEVELOPMENT IN PICKLING CUCUMBERS. Calif. Agr. 23(2): 4-6.

____ and ZAHARA, M. B.
1968. GROWING PICKLING CUCUMBERS FOR MECHANICAL HARVESTING. Calif. Agr. Expt. Sta. and Ext. Serv. AXT-270, 16 pp.

SKREBTSOVA, N. D.
1960. [THE UTILIZATION OF MELLIFEROUS BEES FOR HYBRIDIZATION PURPOSES OF VEGETABLE (CUCUMBER) CULTURE.] In Nauchno-Issled. Inst. Pchelovod. Nauchnolssled, lnst. Ovoshchnogo Khoz., pp. 21 - 30. [ In Russian. ]

____ 1964. [USE OF POLLINATING ACTIVITY OF HONEY BEES FOR DEVELOPING HYBRID VEGETABLE SEED.] Trud. Nauch Issled. Inst. Pchelovod. Selsk. Khoz. Rybnoe, pp. 223-245. [In Russian, English summary.]

STEINHAUER, A. L.
1970. HONEY BEE POLLINATION OF CUCUMBERS IN MARYLAND. Amer. Bee Jour. 110: 12 - 13.

____ 1971. THE POLLINATION OF CUCUMBERS IN MARYLAND. Amer. Bee Jour. 111: 224-225.

STEPHEN, W. A.
1970a. HONEY BEES FOR CUCUMBER POLLINATION. Amer. Bee Jour. 110: 132-133.

____ 1970b. CUCUMBER POLLINATION - MEETING THE CHALLENGE EFFECTIVELY. In The Indispensable Pollinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp. 110 - 111.

STOUT, B. A., LONG, M. M. DE, PETTENGILL, D. H., and RIES, S. K.
1964. A ONCE-OVER MECHANICAL HARVESTER FOR PICKLING CUCUMBERS. Mich. Agr. Expt. Sta. Quart. Bul. 46: 420-430.

STRONG, W. J.
1931. PARTHENOCARPY IN THE CUCUMBER. Sci. Agr. 12: 665-669.

SZABO, T. I., and SMITH, M. V.
1970. THE USE OF MEGACHILE ROTUNDATA FOR THE POLLINATION OF GREENHOUSE CUCUMBERS. In The Indispensable Pollinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp. 95 - 105.

TSYGANOV S. K.
1953. [REMARKS ON THE POLLINATING ACTIVITIES OF HONEY BEES.] Uzbek. Akad. Nauk. Inst. Zool i Parasitol. Trud. t(l): 91-122. [In Russian.]

UNIVERSITY OF ARIZONA.
1970. MELONS AND CUCUMBERS NEED BEES. Ariz. Agr. Expt. Sta. and Coop. Ext. Serv. Foider 90, n.p.

WARREN, L. O.
1961. POLLINATING CUCUMBERS WITH HONEYBEES. Ark. Farm Res. 10(2): 7.

____ 1967. POLLINATTON OF PEACHES AND CUCUMBERS. Apiary Bd. Bul. (Ark.) 4(4): 1 - 2.

WHITAKER, T. W., and JAGGER, I. C.
1937. BREEDING AND IMPROVEMENT OF CUCURBITS. U.S. Dept. Agr. Yearbook 1937: 207-232.

ZAHARA, M., and SIMS, W. L.
1966. ONCE-OVER MECHANICAL HARVESTING FOR CUCUMBERS. Calif. Agr. 20(1): 9-10.

EGGPLANT
Solanum melongena L., family Solanaceae
The eggplant is a minor cooked vegetable crop in the United States. Florida with 2,350 acres and New Jersey with 1,400 acres in 1969 accounted for the bulk of the acreage, which was valued at $4,112,000. However, the plant is grown in home gardens in most areas of the country where there is a long, warm growing season. The average planting in Florida was 42 acres with a yield per acre of 565 bushels, for which the grower obtained an average of $1,310 per acre (Brooke 1970). The value of the 1969 crop in the U.S. was estimated by Brooke (1970) at $5.5 million.

Plant:
The eggplant is a much-branched, gray-green annual 20 to 50 inches high and appears somewhat like the pepper plant but is much coarser. The simple, thick, 6 to 15-inch leaves, are more or less oval, with the undemeath portion covered with thick, white woolly, sometimes spiny hairs. It is grown in rows and cultivated in a manner similar to that for peppers and tomatoes. The egg-shaped, purple fruit is usually harvested when near full size, 3 to 6 inches in diameter (fig. 107).

A fruit may have as many as 2,500 seeds (Odland and Noll 1948). Fruits are sometimes produced with few or no seeds, but they are hard and undesirable.

[gfx] FIGURE 107. - Eggplant, showing flower buds and fruit almost ready for harvest.

Inflorescence:
The 1 l/2 to 2-inch violet flowers of the eggplant are in two- or three- (rarely five) flowered cvmes. They may be perfect (Sambandam 1964) or hermaphrodite (Jones and Rosa 1928*). They develop opposite or near opposite the leaves instead of in the leaf axils as in most plants. The six to 20 anthers form a conelike tube around the style (fig. 108), and they dehisce at the terminal pores in a manner similar to that of the tomato flower, which favors self-pollination (Kakizaki 1924). However, the stigma ultimately projects beyond the anthers, where pollinating insects are more likely to contact it. This position affords ample opportunity for cross-pollination (Hawthorn and Pollard 1964*). The flower remains open 2 to 3 days without closing at night (Kakizaki 1924). It is visited by pollinating insects largely, if not exclusively, for pollen. Smith (1931) found that single flowers are less likely to shed than those on multiple cymes. Whether this is associated with pollination or some other factor is not clear.

[gfx] FIGURE 108. - Longitudinal section of eggplant flower, x 6. Dotted areas indicate variation in length of style and in positions of stamens. Inset shows pores of anther tubes enlarged.

Pollination Requirements:
Bailey (1891) noted that artificial pollination always resulted in fewer seeds than natural pollination even when an excess of pollen was applied. He stated that with hand pollination a few seeds were produced at the apex of the fruit, but most of the ovules remained undeveloped. Jones and Rosa (1928*) reported that plants grown in a screened house isolated from insects were nonfruitful, and that flowers emasculated and left to natural pollination rarely set fruit. This indicated that the plant is not self-fruitful, that wind is not a factor in fruit set but that insects are required to transfer the pollen to the stigma in appropriate amounts and at the right time. The relative time period of pollen transfer for most effective fertilization of a flower has not been determined.

Jasmin (1964) reported that male-sterile plants have been found, in which the anthers do not dehisce. Such plants must be insect pollinated and might be used in the production of hybrid plants. Capinpin and Alviar (1949) reported that hybrids fruited earlier than the parents. Baha-Eldin et al. (1968) concluded that hybrid vigor was strongly manifested in total yield and number of fruit per plant, which would justify the utilization of heterosis in eggplant. Kakizaki (1931) reported that in most of his crosses the first harvesttime was earlier, and production exceeded the best parent by 17 percent. Hybrid eggplants are now being produced commercially by the use of this male sterility factor.

Pollinators:
Wind is not a factor in eggplant pollination, and vibration of the blossom will not cause a sufficient deposit of pollen on the stigma. The eggplant does not self without the aid of bees or man (Kakizaki 1924). The pollinating insects on eggplant have never been studied. Pammel and King (p. 606,1930*) reported that bumble bees were common on the flowers at Ames, Iowa, but no honey bees came to the flowers. Workers dealing with this crop have tended to overlook the insect visitors, but the amount of crossing recorded by different ones indicates that insect visitation occurs in relative abundance. Sambandam (1964), for example, stated that 30 to 40 percent of the fruit set is attributed to pollination by contact, gravity, and wind, the rest to insects, and he reported that crossing on the same plant (in India) ranged from 0.7 to 15 percent, but he made no mention of the insect pollinators responsible for the set or crossing. Kakizaki (1924) reported 0.2 to 46.8 percent cross-pollination. Pal and Taller (1969) likewise discussed pollination of eggplant, and stated that within the variety the number of seeds per fruit is higher in cross-pollinated than in selfed plants, but substantially lower than in open-pollinated plants. No mention is made of the pollinating insects responsible for the better effect on the open-pollinated flowers.

Kakizaki (1924) concluded that bees or man are necessary in the pollination of eggplants.

Pollination Recommendations and Practices:
If male-sterile plants are grown for the production of hybrids, the pollinating insects are essential and should probably be present in relatively large quantities. Even if fertile varieties are grown for fruit production, the meager evidence available strongly indicates that a goodly supply of pollinating insects should be available in the field.

LITERATURE CITED:
BAHA-ELDIN. S. A., BLACKHURST, H. T., and PERRY. B. A.
1968. THE INHERITANCE OF CERTAIN QUANTITATIVE CHARACTERS IN EGGPLANT (SOLANUM MELONGENA L.). H. INHERITANCE OF YIELD, FRUIT NUMBER AND FRUIT WEIGHT. Amer. Soc. Hort. Sci. Proc. 92: 490-497.

BAILEY. L. H.
1891. EXPERIENCES WITH EGGPLANTS. N.Y. (Ithaca) Agr. Expt. Sta. Bul. 26, 26 pp.

BROOKE, D. L.
1970. COSTS AND RETURNS FROM VEGETABLE CROPS IN FLORIDA SEASON 1968-69 WITH COMPARISONS. Fla. Agr. Expt. Sta. Agr. Econ. Rpt. 2, 34 pp.

CAPINPIN. J. M., and ALVIAR, M. A.
1949. HETEROSIS IN EGGPLANT. Philippine Agr. 33: 126 - 141.

JASMIN, J. J.
1954. MALE STERILITY IN SOLANUM MELONGENA L.: PRELIMINARY REPORT ON A FUNCTIONAL TYPE OF MALE STERILITY IN EGGPLANTS. Amer. Soc. Hort. Sci. Proc. 63: 443 - 446.

KAKIZAKI, Y.
1924. THE FLOWERING HABIT AND NATURAL CROSSING IN THE EGG- PLANT. Japan Jour. Genet. 3: 29 - 38.

____ 1931. HYBRID VIGOR IN EGG-PLANT AND ITS PRACTICAL UTILIZATION. Genetics 16: 1-25.

ODLAND, M. L., and NOLL. C. J.
1948. HYBRID VIGOR AND COMBINING ABILITY IN EGGPLANTS. Amer. Soc. Hort. Sci. Proc. 51: 417 - 422. PAL, G., and

TALLER. M.
1969. [EFFECTS OF POLLINATION METHODS ON FERTILIZATION IN EGGPLANT (SOLANUM MELONGENA L.).] Acta Agron. Acad. Sci. Hung. 18(3/4): 307-315. [In Hungarian.] Abstract in Biol. Abs. 52(11) 58979: 5925. 1971.

SAMBANDAM, C. N.
1964. NATURAL CROSS-POLLINATION IN EGGPLANT (SOLANUM MELONGENA). Econ. Bot. 18(2): 128 - 131.

SMITH, O.
1931. CHARACTERISTICS ASSOCIATED WITH ABORTION AND INTERSEXUAL FLOWERS IN THE EGGPLANT. Jour. Agr. Res. 43(1): 83-94.

ENDIVE
Cichorium endivia L., family Compositae
Endive is a green leafy vegetable crop cultivated in the United States on a few thousand acres. It is biennial in seed production characteristics. Most of the seed is produced in California (Hawthorn and Pollard 1954*).

Plant:
Endive forms a large taproot and a rosette of leaves before producing the seedstalk, which elongates the second year. As a vegetable, the leaves are harvested when tender and are used primarily in fresh salads. Culture is similar to that of lettuce; the seeds are planted in the fall, and seeds are harvested the following early summer. As in lettuce, the seed heads on the plant do not mature uniformly so some shattering occurs when the seeds are harvested. Seed yields of 200 to 600 lb/acre for the smooth cultivars, 30 percent less for the curled cultivars can be expected (Griffiths et al. 1946*, Hawthorn and Pollard 1954*, Jones and Rosa 1928*).

Inflorescence:
The composite flower head is 1.0 to 1.5 inches across and is made up of 18 to 20 pale blue florets. The head opens early in the morning and closes before noon (similar to chicory). Numerous flower heads occur on the somewhat branched seedstalk.

Pollination Requirements:
Jones and Rosa (1928*) stated that the flowers of endive are perfect and mostly self-pollinated. Rick (1953) said that the flower is self-compatible. However Anderlini (1956) reported that better results were obtained in producing seed from cross-pollination of flowers than by self-pollination, which indicates that cross-pollination would at least be beneficial in seed production.

Pollinators:
No attention has been given to the pollinators of endive flowers. Considering the relatively few hours the flower is open, if insect pollination is utilized, the population of the pollinators on the flowers should be high.

Pollination Recommendations and Practices:
None.

LITERATURE CITED:
ANDERLINI, R.
1956. [FERTILIZATION IN SALAD PLANTS.] Sementi Elette 2(7): 63-65. [In Italian, English abstract.]

RICK, C. M.
1953. CHICORY-ENDIVE HYBRIDIZED. Calif. Agr. 7(9): 7.

LEEK
Allium porrum L., family Amaryllidaceae
Leek, the national flower of Wales (Patton 1968) (see "Onion"), is another minor crop. Only a few acres are devoted to seed production.

Plant:
The leaves of the biennial leek are flat, solid (pithy), and thick. The bulb is only slightly swollen, giving the stem and bulb a tubular appearance. 'Large American Flag' is the most popular cultivar (Knott 1949, Patton 1968). The growing of leek seed is well suited to the mild climate of Vancouver Island, British Columbia (Adamson 1960). It is mild in flavor and is used both raw and cooked, similar to onions.

Inflorescence:
The seedstalk is 3 to 4 feet tall, terminated by a single umber to 41/2 inches across, and contains several thousand bell-shaped florets (Hawthorn and Pollard 1954*). The flowers are protandrous, the inner three anthers dehiscing first, then the outer ones, after which the style elongates and the stigma becomes receptive (Knuth 1909, p. 445).

Pollination Requirements:
Apparently similar to onions.

Pollinators:
Honey bees, bumble bees, "bees," flies, and "insects chiefly" have been mentioned as pollinators (Hawthorn and Pollard 1954*, Jones and Rosa 1928*, Minderhoud 1951, Sanduleac 1961). Sanduleac (1961) stated that bees increased the seed crop 8 to 10 times.

Pollination Recommendations and Practices:
None.

LITERATURE CITED:
ADAMSON, R. M.
1960. THE EFFECT OF GERMINATION OF DRYING LEEK SEED HEADS AT DIFFERENT TEMPERATURES. Canad. Jour. Plant Sci. 40(4): 666-671.

KNOTT, J. E.
1949. VEGETABLE GROWING. 314 pp. Lea and Eebiger, Philadelphia.

MINDERHOUD, A.
1951. [THE "FIXATION AREAS" OF INSECTS IN RELATION TO PLANT BREEDING.] Tuinbouw Meded. 14: 61 - 70. [In Dutch, English summary. ]

PATTON, I. E.
1968. PLANT LEEKS - THEY'RE DEPENDABLE. Organic Gard. Farming 15(1): 110-111.

SANDUBEAC, E.
1961. [THE POLLINATION OF VEGETABLE SEED PLANTS.] Apicultura 14: 25 - 26. [In Romanian, English summary.]

LETTUCE
Lactuca Sativa L., family Compositae
Lettuce is a major U.S. vegetable crop grown on 234,440 acres in 1970 and valued at about $223 million. California produced more than half of the crop (146,00O acres) with Arizona second (50,900 acres). About 2,300 acres were devoted to lettuce seed production, mostly in California. About 2 million pounds of seed were imported.

Plant:
Lettuce is an annual, grown from seed for its succulent leaves, which form a head that is harvested a few months after the seed is planted. About a month after the head forms, if lettuce is not harvested, the stem within the head elongates and branches to produce the inflorescence, which is 2 to 4 feet high. The seed is produced by the flowers of the inflorescence. From 1/4 to 11/2 pounds of seed are planted per acre. An acre yields 300 to 800 pounds of seed (Foster and Van Horn 1957, Griffiths et al. 1946*, Hawthorn and Pollard 1954 *), depending on the cultivar and method of harvest. The seeds are planted in rows 18 to 22 inches apart and thinned to 12 to 14 inches in the row. The heads are sometimes mutilated to permit the flowering stem to extrude and elongate.

Inflorescence:
This many-branched plant, with numerous leaves near its base, is relatively leafless toward the terminal. The terminal of the inflorescence is primarily a panicle or cluster of yellow flowering heads. Each head is about one-half inch long and is surrounded by a series of overlapping bracts called the involucre. A head contains 10 to 25 florets (fig. 123) that develop simultaneously. The floret ovary is one celled and produces only one seed (actually a fruit called achene), thus a head may produce 10 to 25 seeds (Hawthorn and Pollard 1954*). All of the florets in a head open on the same day, early in the morning, and close shortly afterwards, never to reopen. In some instances, they are only open one-half hour (Purseglove 1968*, Jones and Rosa 1928*, Thompson 1933), but remain open longer on cool cloudy days, sometimes until 2 p.m.

Flowering on a plant may continue for 2 months or longer. A seed ripens 11 to 13 days after the flower opens (Jones and Rosa 1928*). Seeds left too long on the plant may shatter and be lost. Therefore, if all of the seeds are to be saved, the heads must be shaken over a bag at intervals. Usually, the plant is cut at the peak of seed setting, and the bulk of the ripe seeds are salvaged.

The lettuce flower is usually considered to be self-pollinated (Watts 1958, Thompson et al. 1958, Oliver 1910, Jones 1927, Jones and Rosa 1928 *, Hawthorn and Pollard 1954*). The method of self-pollination was described by Knuth (1908*, p. 690), who stated that the style emerges through the anther tube and branches when it is about 2 mm above the tube. These two branches curl back upon themselves, usually make contact with pollen grains on the sides of the style, and self-pollination results. The pollen is pushed out of the anther tube by the brushes on the style and is easily available to bees. There is no evidence in the literature that lettuce secretes much, if any, nectar, although Jones and Rosa (1928*) indicated in a sketch that a nectary exists at the base of the style. Also, Jones (1927) and Thompson (1933) stated that the bees Agapostemon texanus, Californicus crawford, and Halictus spp. collect "mostly" pollen, indicating that some nectar may be collected also.

Besides honey bees and the above-mentioned wild bees, various other insects have also been reported on the lettuce flowers. Knuth (1908*, p. 690) reported "various flies." Watts (1958) reported various species of hover-fly and a few butterflies, although he was unsuccessful in getting hover-flies to pollinate heads enclosed in muslin bags. Jones and Rosa (1928*) mentioned flies and several species of short-tongued bees. Hawthorn and Pollard (1954*) stated that the flowers are frequently visited by wild bees and other insects. Honey bees have been observed by the author collecting pollen from lettuce flowers in southwestern Arizona.

[gfx] FIGURE 123. - Lettuce flower. A. Longitudinal section, x 10; B, longitudinal section of one floret, x 30.

Pollination Requirements:
The structure of the lettuce flower encourages self-pollination and the plants are self-compatible; therefore, seeds can be produced on plants bagged to exclude insects. The pollen is not windblown. However, cross- pollination has been observed (Thompson 1933, Thompson et al. 1958, Watts 1958). To determine if insects affected the transfer of pollen, Jones (1927) compared stigmas of flowers exposed to open pollination with those bagged to exclude pollinating insects. He observed 70 bagged flowers, of which 58 had no pollen grains on their stigmatic surfaces, and the other 12 flowers bore only one to seven grains. However, of 70 flowers exposed to pollinating insects, all stigmas had from 4 to 51 grains of pollen present. This showed that pollinating insects contribute to the effective transfer of pollen to the stigma, within the flower and likely between flowers. As a result, Jones and Rosa (1928*) concluded that cross-pollination between plants may be much more frequent than was formerly supposed. When Flemion and Henrickson (1949) bagged dill plants with insect pollinators present, they obtained 1,000 seeds per umber compared with only 59 per umber on plants caged without insects present. If the authors had performed a similar test on lettuce, the test by Jones (1927) indicates that they might have obtained similar results.

Furthermore, the discovery of male sterility in lettuce (Ryder 1963, 1967) opens the way for production of hybrid lettuce seed, if means can be found to effectively transfer the pollen from male-fertile to the male- sterile plants. So far, the only conceivable way is to have insects transfer the pollen. Without the presence of pollen on the male-sterile plants, the insects must be enticed there by the presence of nectar. Because the flower is only open briefly, the concentration of insects would need to be high for effective cross-pollination.

Pollinators:
Although flies, wild bees, and butterflies have been mentioned as visitors to lettuce flowers, none of them are present in commercial lettuce fields in a sufficient quantity when desired to cross-pollinate male-sterile lines necessary for hybrid seed production.

Honey bees can be supplied at any time by commercial beekeepers and honey bees are concerned with collecting nectar. Therefore, they would appear to be the only potential insect at present that would be suitable for pollinating the male-sterile plants.

Pollination Recommendations and Practices:
None.

LITERATURE CITED:
FLEMION, F., and HENRICKSON, E. T.
1949. FURTHER STUDIES ON THE OCCURRENCE OF EMBRYOLESS SEEDS AND IMMATURE EMBRYOS IN THE UMBELLIFERAE. Boyce Thompson Instit. Contrib. 15(6): 291-297.

FOSTER, R. E., and VAN HORN, C. W.
1957. LETTUCE SEED PRODUCTION IN ARIZONA. Ariz. Agr. Expt. Sta. Bul. 282, 22 pp.

JONES, H. A.
1927. POLLINATION AND LIFE HISTORY STUDIES OF LETTUCE (LACTUCA SATIVA L.). Hilgardia 2: 425-448.

OLIVER, G. W.
1910. NEW METHODS OF PLANT BREEDING. U.S. Dept. Agr. Burl Plant Indus. Bul. 167, 39 pp.

RYDER, E. J.
1963. AN EPISTATICALLY CONTROLLED POLLEN STERILE IN LETTUCE (LACTUCA SATIVA L.). Amer. Soc. Hort. Sci. Proc. 83: 585 - 595.

______ 1967. A RECESSIVE MALE STERILITY GENE IN LETTUCE (LACTUCA SATIVA L.). Amer. Soc. Hort. Sci. Proc. 91: 366-368.

THOMPSON, R. C.
1933. NATURAL CROSS-POLLINATION IN LETTUCE. Amer. Soc. Hort. Sci. Proc. 30: 545 - 547.

______WHITAKER, T. W., BOHN, G. W., and VAN HORN, C. W.
1958. NATURAL CROSS POLLINATION IN LETTUCE. Amer. Soc. Hort. Sci. Proc. 72: 403 - 409.

WATTS, L. E.
1958. NATURAL CROSS-POLLINATION IN LETTUCE, LACTUCA SATIVA L. Nature 181(4615): 1084.

MUSKMELON
Cucumis melo L., family Cucurbitaceae

The muskmelons grown commercially in this country were classified by Whitaker (1970) into "varieties." Variety reticulatus Naud. includes the cantaloupes and 'Persian' melons, and variety inodorus Naud. includes the Casabas and the Honey Dews. There are numerous cultivars of each.

Muskmelons are grown in most States, but more than one half the acreage is in California. The bulk of the muskmelon crop is cantaloupes, combined with a small acreage of Casabas and 'Persians', which amounted 111,800 acres in 1970. Honey Dews were produced on 13,200 acres. The combined farm value of all muskmelons was $93.3 million.

Plant:
Muskmelons are trailing annuals, the vines, if unchecked, spreading to about 10 feet. The leaves are 4 to 8 inches across, and their 6- to 10- inch upright stem enables them to form a protective arborlike canopy over the flowers and fruit. The one to six melons per plant develop from the yellow hermaphrodite flower in the axis of the leaf. At maturity, about 6 weeks after the bloom appeared, the round to oblong melon is 4 to 8 inches in diameter. The frost-susceptible plants are usually grown in 6-foot rows, 4 to 24 inches apart in the row, with the best yield from plants 6 to 12 inches apart in the row (Pew 1952, Davis and Meinert 1966).

All forms of C. melo readily hybridize, as for example the 'Pershaw', which is thought to be a cross between the 'Persian' melon and the 'Crenshaw', Casaba, or the 'Honey Ball', which is a cross between the Honey Dew and the 'Texas Cannon Ball'. Rosa (1926) reported some self- incompatibility in the 'Persian' and the Honey Dew. The bulk of the discussion which follows will concern cantaloupes.

Inflorescence:
Most American cultivars of muskmelons are andromonoecious, bearing staminate and hermaphrodite flowers on the same plant (fig. 129). The numerous staminate flowers are borne in axillary clusters of three to five in all axillary positions not occupied by the few slightly larger solitary hermaphrodite flowers. The flowers are 3/4 inch to 1 1/2 inches across, with five petals united to slightly beyond the staminal column, then separated and broadly spreading (Whitaker and Davis 1962*). Griffin (1901) reported 512 staminate and 42 hermaphrodite cantaloupe flowers per vine. McGregor (1951 ) showed, however, that this ratio varies depending upon bee activity and fruit set. When bees were excluded, no fruit set and the ratio was one hermaphrodite to four staminate flowers, but in caged and open plots visited by bees the ratio was one hermaphrodite to 10 staminate flowers. Apparently, failure of the plant to set fruit stimulates production of a higher proportion of hermaphrodite flowers.

The staminate flower, supported on a thin stem, consists of the corolla, a single whorl of five stamens, only a few millimeters long, two pairs of which are united, with the anthers almost filling the small corolla tube. At the base of the corolla, a rudimentary style is surrounded by the nectaries (Judson 1935). The hermaphrodite flower has anthers and a broad, usually three-lobed stigma on a 1- to 2- mm style, the base of which is surrounded by the nectaries. The corolla of the hermaphrodite flower is on the end of the elongated ovary (Jones and Rosa 1928*, Judson 1949).

The muskmelon flower opens some time after sunup, the time depending upon the sunlight, temperature, and humidity. When the temperature is low, the humidity is high, or the day cloudy, opening is delayed. The flower closes permanently in the afternoon of the same day. Bee activity begins on the flower shortly after it opens, reaches a peak at about 11 a.m., and ceases about 5 p.m. (McGregor and Todd 1952*). At Davis, Calif., the flower opening and attraction for bees is an hour or so later in the day (Mann 1953).

The flower is attractive to bees for both pollen and nectar. Collection of pollen by bees usually ends before noon, but nectar collection continues into the late afternoon. Only about 1 percent as much nectar per acre is secreted by muskmelons as is secreted by alfalfa. Foster et al. (1965) showed that muskmelon plants infected with mosaic viruses produce less nectar than healthy plants.

[gfx] FIGURE 129. - Longitudinal section of muskmelon flower, x4. A, Hermahphrodite; B, staminate.

Pollination Requirements:
The isolation of muskmelon plants from pollinating insects and the caging of bees on the plants have proven that hermaphrodite flowers are incapable of performing self-pollination. The pollen must be transferred from the anthers to the stigma by insects (Alex 1957a, b; Bohn and Davis 1964; Mann 1953,1954; Mann and Robinson 1950; McGregor and Todd 1952 *,1952; and McGregor et al. 1965).

Muskmelons with fewer than 400 seeds are usually so small they are classed as culls. At least one viable pollen grain must be deposited on the stigma and fertilize an ovule if a seed is formed. The effective period in which this pollen can be deposited on the stigma is no more than a few hours in the morning, and if the temperature is high, the period may be only a few minutes. Single massive deposits of pollen by hand on the stigma are seldom as effective in the setting of fruit as repeated bee visits (Mann and Robinson 1950, Wolf and Hartman 1942). Muskmelon flowers are self-fertile (although not self-fertilizing), but when pollen comes from a different plant, the fruit that results may be slightly heavier (Rosa 1926). Also, a high correlation exists between the number of seeds in a muskmelon and its size - the more seeds the larger the fruit. Increased bee visitation is associated with greater number of seed.

Pollinators:
Tontz (1944) mentioned ants as possible pollinators of muskmelons and squash. Annand (1926) indicated that thrips might be pollinators of muskmelons, but Tsyganov (1953) considered one bee equal to 11,000 thrips. The value of thrips and ladybird beetles was discounted by McGregor and Todd (1952*, 1952) when they obtained no set of marketable cantaloupes in cages where honey bees were excluded and these insects were common, but a satisfactory set in cages supplied with bees. Bohn and Mann (1960) showed, with the mutant nectarless, the dependence of high muskmelon yields on honey bee pollination. The value of bees as pollinators of muskmelons, stated by Beattie and Doolittle (1926), Ivanoff (1947), Rosa (1927), and Rosa and Garthwaite (1926) is now firmly established. Because of their relative abundance in commercial fields and their attraction to muskmelon flowers, honey bees are the most important of the muskmelon pollinators. Beattie and Doolittle (1926) stressed the need for bees on muskmelons grown in greenhouses.

Honey bees visit muskmelon flowers as soon as the flowers open (fig. 130). They collect both nectar and pollen, move freely from flower to flower and plant to plant, and continue visiting the flowers until late afternoon. McGregor et al. (1965) showed that a honey bee visit to each flower about every 15 minutes is desirable for maximum fruit set. They calculated that one bee for each 10 hermaphrodite flowers is necessary to provide this rate of visitation. Whitaker and Bohn (1952) showed that variations in visits by honey bees occur between plants sometimes only a few feet apart if there is a variation in the microclimate around the plants. This means that many flowers must receive more visits than necessary if all are to receive the optimum number.

Growers prefer muskmelon fruit that is produced near the base of the plant. Such fruit is referred to as "crown set," or the set of fruit from the hermaphrodite flowers on the first to third spur. When there is heavy bee activity, a heavy crown set results (Rosa 1924, Whitner 1960). Such fruits are sweeter (McGregor and Todd 1952*, 1952), and are usually more oval than later fruits, which tend to be oblong.

Iselin et al. (1974) grew cantaloupes in an air-inflated plastic greenhouse. Their plants, shielded from bees, set no fruit, but plants visited by bees fruited normally. Bee foraging activity was similar to activity outside the greenhouse. They also reported that raising the CO₂ content of the air in the enclosure increased the soluble solids (sugar content) of the ripe melons from 8 to about 12 percent.

Usually, the set of one or two fruits prohibits the set of further fruit until the first ones mature. Thus, when McGregor and Todd (1952) excluded bees for 3 weeks after initial flowering and then permitted unlimited visits to the flowers, 80 percent of the marketable fruit was set within the first 3 days, but the total production was not significantly different from production in cages where bees were constantly present. The fruits that set later were less sweet than crown-set fruit.

In studies on hybrid vigor in muskmelons, Foster (1963, 1967,1968a, b, c), Foster and Levin (1967), and Bohn and Davis (1957) found that F₁ hybrids produced twice as much fruit as commercial cultivars, and other characters were improved. Bohn and Whitaker (1949) reported male sterility in the muskmelon, a character useful in hybrid seed production. Munger (1942) also showed that utilization of hybrid vigor was practical. In the utilization of hybrid vigor, pollination by bees is essential.

Taylor (1955) studied the production in 37 muskmelon fields in the Salt River Valley of Arizona in relation to proximity to honey bee colonies. In 20 fields with an average of one-half colony per acre within a mile, production was 1.06 melons per plant and 242 crates per acre. In 17 fields with no hives of bees in the "visible vicinity," production was only 0.67 melon per plant and 161 crates per acre. Honey bees were visiting muskmelon flowers in