FIBROVASCULAR TISSUES: RAYS 91 



sion that wherever the compound or diffuse types of rays are 

 present in members of these groups they have been derived from 

 an earlier condition of aggregation. The type of ray structure 

 is not strictly related to any particular organization of the flower, 

 since amentaceous, archichlamydeous, and metachlamydeous fami- 

 lies present to an almost equal extent the various categories of 

 rays. In a general way it may, however, be stated that the diffuse 

 condition of the rays is characteristic of arboreal forms, while the 

 compound condition occurs mainly in vines and herbs. 



