INTERDEPENDENCE OF ORGANISMS 



35 



These brief studies of the relations between flowers and 

 insects should have made it apparent that we have with us 

 all grades of association from the most casual contact to 

 mutual dependence, and that we have all grades of fitness 

 on both sides : further that while the adaptations are often 

 wonderfully intricate and fit, they rarely work perfectly, 

 and may even wholly miscarry. And while gratified in 

 observing that they often work with delightful precision, 



FIG. 27. Flowers and fruit of the violet. The ordinary blue 

 flower and a seed capsule (from a hand pollinated flower) 

 shown above; a row of clistogamus flowers shown below; 

 the lowest one in full bloom. 



we should not overlook the fact that the simpler plans 

 suffice for the maintenance of the species that are less 

 specialized. 



II. GALLS. 



Galls are abnormal growths of plant tissues occasioned 

 by stimuli external to the plant itself. The stimuli are 

 furnished by a great variety of insects, by a few parasitic 



