MANY VEGETABLES do not require pollination to produce an edible crop, but of these, carrots, radishes, turnips, cabbage, celery, and many others require insect pollination for seed production. Both pollination and seed formation are essential in the production of the edible part of the pickling cucumber, cantaloup, and watermelon.

Pollination of all sections of the compound ovary is evidently necessary for proper shape and quality of melons, as the deformed part of an incompletely pollinated cantaloup not only lacks seed but is also poor in sweetness and flavor. Honey bees are employed in the commercial production of the seed and fruit of several vegetable crops.

Varietal crossing is generally undesirable in producing seeds for the propagation of vegetable crops. Hence the Department of Agriculture regulations require that in the production of seed of many vegetables the plots of the different varieties must be at least one-fourth mile apart. An even greater distance would be safer because pollen grains are always found on the honey bee and its flight range exceeds one-fourth mile.

Cucumbers, muskmelons, watermelons, pumpkins, and squash have similar floral structures. The group-cucurbits generally is characterized by having male and female blossoms on different parts of the same plant. Such an arrangement obviously requires insects for the transfer of pollen, as the plants are not wind-pollinated. Most varieties of cucurbits are self-and interfertile when pollinated by hand.

Honey bees are widely used in greenhouse and field production of cucumbers. Because the individual flowers are open for only a short time, a heavy concentration of bees is advisable whether the cucumbers are grown for the fresh market, for pickling, or for seed.

Watermelons and muskmelons often produce bisexual or complete flowers, instead of separate pistillate and staminate flowers. The complete flowers, however, do not fertilize themselves, and honey bees are as essential in their pollination as in the pistillate flowers.

Cabbage and the closely related cabbage-like plants as cauliflower, broccoli, and brussels sprouts require cross-pollination by insects for good seed yields. Varieties of cabbage display various degrees of self-incompatibility. Cross-incompatibility is also common.

Bees are effective agents in cross-pollination. Attempts to bring about self-pollination have had little success. Besides honey bees, cuckoo bees, leaf-cutting bees, mining bees, bumble bees, and bee flies are attracted to cabbage flowers. Some are said to work at lower temperatures than the honey bee. Because cabbage for seed production is often grown in a cool location or during cool weather, some of these insects may be individually more effective than the honey bee in its pollination. The optimum temperature for pollen germination, however, is about 68 F., and bees are active in the field at temperatures as low as 60 .

ENGLISH HOLLY trees bear their pistillate and staminate flowers on separate plants. Although a small percentage of the pistillate flowers on some trees develop parthenocarpic berries, facilities for cross-pollination are required for commercial crops. The seeded berries resulting from cross-pollination are larger, less subject to premature dropping, earlier maturing, and more resistant to withering after cutting. Bees are attracted to both staminate and pistillate holly flowers to such an extent that, when they are abundant, only one male tree is needed for pollinating 50 pistillate trees. The pollinizers should be selected for their foliage quality as well as their capacity to produce an abundance of viable pollen when the pistillate trees are blooming.

POLLINATION BY HONEY BEES has thus become an essential factor in producing many crops, along with the factors that are taken for granted, such as the preparation of the soil, the sup-Plying of moisture, and cultivation, pruning, and thinning. Because beekeeping is a specialty, just as fruit growing or the production of seeds are specialties, most growers will find it advantageous to rent bees rather than to keep their own. Cooperation between grower and beekeeper thus becomes important and is mutually advantageous.

GEORGE H. VANSELL, an apiculturist in the Department of Agriculture, is stationed at Davis, Calif. He has studied in the University of Kansas, Harvard and Stanford Universities, and the University of California. He has taught in the Universities of Kentucky and California. The activity of bees in collecting nectar and pollen, especially as agents of pollen distribution, has been his chief interest for many years.

W. H. GRIGGS is assistant professor of pomology in the University of California at Davis. He has charge of investigations into the pollination of fruits and nuts. He received his training in pomology in the University of Missouri and the University of Maryland. Dr. Griggs was assistant professor of pomology in the University of Connecticut in 1916 and 1947.