30 



BULLETIN 700, TJ. 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, 



1916 1916 



RABBIT BRUSH 



1916 1915 1916 



OAH-BRUSH AS PEN -FIR 



MONTHLY AND. ANNUAL PRECIPITATION 



RABBIT BRUSH 

 OAK-BRUSH 

 ASPEN -FIR 

 SPFHJCE-FII? 



MONTHLY PRECIPITATION DURING GROWING SEASON 1916 

 FIG. 14. Precipitation record, 1915-1916. 



in th 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. 



