86 PLANT BIOLOGY 



Moreover, in case cross- and self-pollination take place in a 

 given flower, it has been proved that the pollen from another 

 flower will usually grow down the pistil more rapidly than the 

 pollen produced in the same flower, and so in such cases fer- 

 tilization is more likely to result from cross-pollination than 

 from self-pollination. 



96. Cross-pollination by insects. From our study of the 

 pansy we learned that insects are attracted by bright colors 

 and sweet odors. By many observations biologists have 



FIG. 32. A, staminate squash blossom ; B, pistillate squash blossom. 

 (Bailey.) 



learned that most flowers with these characteristics are vis- 

 ited by insects, and that these animals carry pollen from 

 blossom to blossom, thus insuring cross-pollination. Any 

 one familiar with apple, pear, or other fruit trees has seen 

 that at time of blossoming these trees are alive with buzzing 

 bees, and fruit growers know that were it not for these insect 

 visitors their fruit crops would prove a failure. Some 

 plants (the squash, for example) have two kinds of flowers, 

 one kind containing stamens, the other pistils. It is evident, 

 therefore, from what we have already learned that pollina- 



