74 RECIPROCAL NUTRITIVE DISJUNCTIVE SYMBIOSIS 



In many respects insect-pollinated flowers contrast sharply with 

 those that are wind-]wllinated (Fig. 28). The flowers as a rule are 

 not in catkins but rather in inflorescences that are relatively inflexible 

 in the wind. The stamens ha^•e relatively short filaments and are 

 usually not prominently exserted. The pollen, instead of being dry 

 and smooth, as in anemophilous flowers, is often rough with spines 

 or other protuberances, or viscid, or both. This causes the grains 



Fig. 28. — Frasera speciosa, with insect-pollinated flowers. 



to stick together in masses, renders them less easily blown about by 

 the wind, and adapts them admirably to sticking to the legs and 

 bodies of insects as well as to stigmatic surfaces. 



Flowers that are wide open and have their parts freely exposed can 

 usually be pollinated by most any kind of visiting insect. They often 

 have numerous stamens and produce pollen as abundantly as many 

 wind-pollinated species. Those that have the pollen partly or 

 wholly concealed in tubular or otherwise partly closed corollas, how- 

 ever, usually have few stamens and do not produce pollen abun- 



