EXERCISE 120 



Problem. What is there about flowers that makes possible the distribution of their pollen by insects? 



What to use. As in previous exercise. 



What to do. Examine the stamens, pollen, stigmas, and envelope of many different wild and 

 cultivated flowers, looking out especially for flowers around which insects are hovering. Note the rela- 

 tive position of the anther and the stigma and the character of the pollen that would make distribution 

 by insects probable. Note what there is about the structure of the flower as a whole that would make 

 the visits of insects likely. 



Record. Make a list of plants that you think are probably insect-pollenated, illustrate by drawings, 

 and describe the characteristics that lead to your conclusions. 



Questions. 1. What practical use is made of the fact that insects make their food stores out of 

 flower nectar ? 



2. What plants secrete nectar without getting their pollen transferred by insects ? 



3. Can you find insects visiting flowers without serving as pollen carriers ? 



4. What plants with odorous and conspicuous flowers are pollenated without the aid of insects ? 



[129] 



