SOIL AND SUBSOIL. 



169 



hot " norther " will often in a short time not only dry the 

 plowed soil, but will heat it to such extent as to actually bake 

 the roots it harbors. Under the same weather-conditions an 

 adjoining field, properly plowed, may almost wholly escape 

 injury. 



Comparison of root development in the arid and humid 

 regions. Figures 28, 29 given here show the differences as 



FIG. 29. Prune Tree on Peach Root, at Niles, Cal. 



actually seen in the case of fruit trees as grown in Wisconsin 

 and California, respectively, both in the absence of artificial 

 water-supply. 



Adaptation of humid species to arid conditions. Figures, 

 in No. 30, show the root systems respectively of the riverside 

 grape (Vitis riparia} as grown in the Mississippi Valley states, 

 and the natural development as found in the Rock grape of 



