468 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1961 



fruit with its own pollen. The blossom of a Jonathan apple must 

 receive pollen from an entirely different variety of apple. This in- 

 troduces an interesting complication, Apple pollen is heavy and 

 sticky; it cannot be carried by the wind. How then is pollen from 

 one tree brought to another which may be many yards away ? There 

 is only one answer — through the medium of insects which live on 

 nectar and pollen. One has only to look into the branches of an apple 

 tree at full bloom to realize that honey bees are the predominating 

 flower visitors and are the agents that put on a set of fruit. 



The mode of reproduction, that is, seed or fruit formation, is slightly 

 different from that of the apple in plants belonging to the cucumber 

 family. Plants such as watermelon, cantaloupe, pumpkin, and cu- 

 cumber, instead of having both sexual elements in the same blossom, 

 contain two kinds of blossoms; one is all female and the other is 

 all male. Here again pollen must be carried from the male flower to 

 the female. 



A small number of hermaphroditic flowers also occur in this family 

 of plants. Here again, since pollen from these plants is sticky and 

 not wind-borne, the indispensable service of pollen-carrying insects 

 is apparent. Crooked cucumbers and flat-sided melons are the result 

 of insufficient pollen coming in contact with the female flowers. A 

 pollen grain is needed for the development of each seed. A well- 

 formed cantaloupe may contain up to 600 seeds, the more seeds the 

 larger and sweeter the melon. How many of us credit the honey bee 

 when we cut into a luscious breakfast melon ? 



There are still other types of plants in which a single plant pro- 

 duces only male flowers, while another plant of the same species bears 

 only female flowers. The wild persimmon and holly are good illus- 

 trations of this type. Since the wind cannot be depended upon to 

 disperse the pollen adequately, insects again come into the picture. 



There are approximately 50 cultivated crops grown in the United 

 States that require insect pollination. In addition to those already 

 mentioned, there are many other important plants — for example, 

 alfalfa, sweetclover, red clover, alsike clover, white Dutch clover — 

 which must have each tiny flower visited by an insect in order to 

 produce seed and thus perpetuate themselves. Pollinating insects are 

 either essential or highly desirable in the production of seeds of many 

 vegetables, such as carrot, onion, cabbage, cauliflower, and brussels 

 sprouts, to name only a few. 



Insect pollination is a "must" in our present-day agriculture, but 

 why is it more important today than it was 30 or 40 years ago ? 



There was a time in the history of agriculture, and not so many 

 years ago either, when it was not uncommon to hull 6 to 10 bushels of 

 red clover or alfalfa seed per acre. It is only rarely that such produc- 



