30 



BULLETIN 700, U. S. DEPARTMENT OF AGRICULTURE. 



The smallest number of heat units above 40° F. and the largest 

 number below 40° F., as shown in figure 4, occur in June and Sep- 

 tember, near the beginning and ending of growth in the two lower 

 types represented. 1 One of the most significant facts brought out 

 in Table 9 is the absence of temperatures below 40° F. for August, 



i 



jj 



19/5 1916 



RABBIT BRUSH 





1916 

 O AH- BRUSH 















* 1.1 



1915 1916 



ASPEN-FIR 































1 



I 



1 



(OCT 

 NOi/. 

 DEC. 



(JAN. 



FEB. 

 MAR 

 APR 

 MAY 

 J UN 

 JUL 

 AUG. 

 .SEP 



1915 1916 



5PRUCE-FIR 



MONTHLY AND. ANNUAL PRECIPITATION 



RABBIT BRUSH 

 OAK-BRUSH 

 ASPEN-FIR 

 SPRUCE-FIR 



MONTHLY PRECIPITATION DURING GROWING SEASON 1916 

 Fig. 14. — Precipitation record, 1915-1916. 



in the oak-brush type. All types considered, July and August are 

 the most favorable months for growth, in so far as it is determined 

 by temperature. 



1 Growth begins in the oak-brush type approximately June 1. In the aspen-fir type 

 the leaves begin to unfold about two weeks later. In the spruce-fir type growth begins 

 between 3 and 4 weeks later than in the oak-brush type. 



