CLIMATE 



51 



prairie country. Table 6 shows the highest and lowest tem- 

 peratures on record for 35 stations in Montana during the six 



Table 5. Average mean temperatures during the months of the 

 growing season and average annual means. 



months of the growing season. Again the figures for western 

 Montana are the most significant as representing a more heavily 

 forested region. But in other parts of the State represented 

 by these figures there are forests locally important, or at least 

 forest species more or less common. While it may be seen that 

 in all sections the maximum may rise to 100 degrees "or more, the 

 minimum for each month falls more often below the freezing 

 point than above it. 



The vital phenomena of plants are mostly confined to tem- 

 peratures above freezing. While it can be shown that certain 

 functions are performed at a diminished rate below 32 degrees 

 F... it is also evident that all functions increase in vigor in geo- 

 metrical ratio from this point up to the optimum. The length 



