MESA AND FOOTHILL VEGETATION 



17 



tribution normal. This is especially true of the past season (spring 

 and summer of 1908). For this reason the records of soil moisture do 

 not show as much as might be desired. They in all probability do not 



Fig. 4. — Soil Map of Long Mesa and Horse Mesa. — The greater part of the 

 area covered by this map has a soil of sandy texture. The shading indicates the relative 

 frequency of boulders and good-sized rocks. Note the very rocky area just at the edge 

 of the mesa. This has a very important relation to the distribution of trees on the mesas. 

 The portions shaded with lines are areas having a fine clay soil formed by the exposure 

 of the underlying shales or limestones. The oblique shading indicated shales, the vertical, 

 limestones. 



show average characteristic differences between habitats, and it is 

 entirely probable that an average yearly distribution such as observed 



