42 



BULLETIN 700, IT. S. DEPARTMENT OF AGRICULTURE. 



length, and stem height, in the aspen-fir association, and (2) the rela- 

 tively high water requirement for the production of a unit of dry 

 matter in the oak-brush type. 



In the case of peas, the number of leaves produced in the aspen-fir 

 type, as compared with the oak-brush and spruce-fir types, respec- 

 tively, is approximately in the ratio of 4, 2, and 1.7. The leaf length 

 of wheat shows a ratio of about 2, 1, and 1.3 in favor of the aspen-fir 



626 



26 



5280 

 26 



3990 



\ 



s 



300 



88 



Oak-brush dspen Spruce-fir 



L eaf length 



A/umber of /eaves 



Water requirement per 



un/f dry matter 



FIG. 21. Water requirements and vegetative growth of wheat in the three climatic types. 



association. In the case of the brome grass practically the same 

 relations exist. 



In each instance the water requirement per unit of dry matter is 

 the highest in the oak-brush type. The fact that the plants were 

 grown for a longer period in the highest and middle stations would 

 naturally imply that they used more total water, but not necessarily 

 that they had a higher water requirement per unit of dry weight. A 

 comparison shows that in the case of wheat and peas the water 

 requirements are very nearly the same in the central and in the 



