110 BIOLOGY FOR BEGINNERS 



agents in pollenation and there is no process for which more curi- 

 ous adaptations have been developed. We shall deal first with 

 those that fit the flower for pollenation by insects. 



Adaptations for Insect Pollenation. The bee and the flower are 

 associated in our minds, of course, but it is not so commonly realized 

 that one could not exist without the other, and that many other 

 insects, besides bees, are just as closely concerned. 



The insect comes to get its food from the sugary nectar which 

 is secreted at the base of the petals ; in getting this, its body catches 

 some of the pollen from the stamens which are shaped for this 

 purpose. When the insect visits the next flower some pollen is sure 

 to be rubbed off on the pistil of that flower, and a new supply 



FIG. 33. Hawk-moth posed before a jimson-weed, Datura stramonium (after 

 Stevens; one-half natural size). 



brushed from the stamens as it crawls out. In this way pollena- 

 tion is accomplished. 



In order that the insects may surely see each flower, they have 

 developed conspicuously colored corolla and attractive odors. 

 They often grow in clusters so as to be easily noticed and visited. 

 After the insect arrives, not only does it find a reward of nectar, 

 but often the flower is shaped to provide a convenient landing 

 place. Colored lines lead to the nectar glands. Stamens and 

 pistils hold their anthers and stigmas in just the proper position so 

 that pollen shall be transferred while the insect is obtaining its 

 sweet reward for unintended labors. 



Nearly every flower has a slightly different scheme for cross 

 pollenation. When we find one with irregular-shaped corolla, we 



