80 REPRODUCTION 



we should remember that it is extremely doubtful if insects cah 

 distinguish shape, size or color for any considerable distance. 



Interesting modifications of their parts are found in many 

 flowers. These facilitate pollination by means of insects, and 

 some flowers are so specialized that certain insects are neces- 

 sary for this work. Among the simplest of these modifications 

 is the long tubular corolla of the morning glories and honey- 

 suckles which make it necessary that their visitors have long 

 beaks or mouth parts by which they can reach the nectar glands 

 at the bottom. The tubular corolla of the red clover is such 

 that it is imperfectly pollinated except by the bumble bee and, 

 therefore, it is practically impossible to grow red clover seed 

 without these insects. The barberry, and some other plants, 

 have stamens of such character that when touched by the in- 

 sect they serve as springs, striking the anthers against its body. 

 The milkweed and other plants are so constructed that masses 

 of pollen may cling to the body of the insect and be carried 

 from flower to flower, losing some pollen with each visit. Beans, 

 peas, and similar flowers have peculiarly shaped corollas which 

 conceal the essential organs, but when the insect settles upon 

 them these parts are exposed and the lower surface of the body 

 brought in direct contact with them. A thorough discussion 

 of the devices for facilitating the pollination by means of insect 

 visitors would require a large volume and then be incomplete, 

 but it is a subject in which any close observer can learn some- 

 thing previously unknown, something not in the books. 



Cross Pollination. — It will be readily seen that sexual 

 pollination is usually accomplished by the pollen of one flower 

 on the stigma of another flower of the same or a different plant. 

 This is known as cross pollitiation and, of course, results in 

 cross fertilization which, as previously stated, is believed, in 

 many cases, to give increased vigor to the new generation of 

 plants. If this is true, we are certainly justified in expecting 

 to find some modifications in nature which prevent self-pollifir 



