110 



COACTION: THE INTERRELATIONS OF ORGANISMS 



role, followed by plants and then by those partnerships in which each 

 plays the part of coactor in some measure. Coactors differ chiefly in 

 habit and form, which are usually related to the various types of coac- 

 tion. This is true to a large degree of the inactive agents (coactees) 

 likewise. Plant coactees may conveniently be subdivided on the basis 

 of the organ or part used for food, material, shelter, etc. 



Figs. 22a and b. — A nest of the hooded warbler (Wilsonia citrina, Bod.) show- 

 ing the use of forest floor leaves in construction. Both are of the same nest, 

 built in a small .sprout of tupelo, 32 inches from the ground. The long slim 

 crotch is filled with a loose wad of dead beech leaves upon which the real nest 

 is built. The neatly compacted rim of dead beech leaves is bound in place with 

 strips of the inner bark of chestnut, of which a plentiful supply is available 

 owing to the activities of the "chestnut blight." The lining is of finely shredded 

 strips of grapevine bark — quite hairlike in character. This nest was so well done 

 from the standpoint of camouflage that one could look directly at it without 

 perceiving its nature. (Photo by Arthur B. Williams, Cleveland Museum of 



Natural History.) 



In number, coactions are practically countless, and all that can be 

 attempted in a preliminary organization of this vast field is to pass 

 in review the frequent, typical, or outstanding examples and to relate 

 these to the community life of the biome, so far as this is feasible at 

 present. In this connection, composite interactions involving more 

 than two species as individuals and especially as groups are peculiarly 



