PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 291 



both experimental and from field observations, are needed in this 

 and other regions before this question can be answered. The 

 illogical neglect of most ecologists in not working in this interest- 

 ing field is to be deplored. However, we must not overlook the 

 fact that the real solution of the problem of adaptation to environ- 

 ment will be solved only when the extent and character of both 

 absorbing and transpiring parts of plants are studied and cor- 

 related. The writer has under way an investigation of the 

 ecological anatomy of the leaves of the plants mentioned in this 

 paper, together with the extent of the transpiring surface. 



Cannon (loc.cit.) points out that for desert plants having gener- 

 alized root-systems it is probable that the penetration of the roots, 

 the character of the soil permitting, is equal to the penetration 

 of rains; also that "the generalized roots are often extremely 

 variable, ranging from a pronounced tap root to a marked develop- 

 ment of laterals, dependent upon soil characters and water 

 relations." No such marked changes as these were discovered, 

 although since the variation in the branching habit is a matter 

 of degree rather than kind, it would be difficult to express 

 the differences in exact terms if indeed these differences had 

 been noticeable. However, the roots of several species showed 

 a marked increase in their output of branches upon leaving the 

 compact soil and entering earthworm burrows. In practically 

 all cases the root tips under such conditions were alive and at 

 least well covered with root hairs, while in the more compacted 

 soils of dry slopes especially, the root tips were often dead and 

 decayed. The cause of these differences is yet to be determined. 

 The differences may be due to the mechanical resistance offered 

 by the soils, or to changed conditions of aeration, or perhaps to 

 both factors acting together. 



These findings of great root depths, correlated with deep soil 

 moisture, bear out Cannon's suggestion of the probability that 

 the longest or the most deeply penetrating roots are found, not in 

 deserts, but where there is considerable rainfall, and where the 

 penetration of rain is considerable and the water table relatively 

 deep. It may be noted here, by way of comparison, that Andro- 

 pogon scoparius at Manhattan, Kansas, penetrates the soil to 



