ECOLOGICAL GROUPS 485 



crowberry (Fig. 363), forms the interior of a nearly closed 

 tube, transpiration is still more hindered. 



Hairy leaves (5) are characteristic of plants of dry climates, 

 as the Mediterranean region, and of dry exposed areas like 



FIG. 366. Part of a euphorbia stem, the branches showing considerable 

 resemblance to those of some cacti 



the higher portions of the great Western plains in this country. 

 Generally the hairs are relatively simple in their structure 

 and do not completely cover the surface. But in many in- 

 stances the hairs assume shield-like or other flattened forms, 

 and they may overlap so as more than to cover the surface 



