40 



BULLETIN 700, U. S. DEPARTMENT OF AGRICULTURE. 



data given for each station represent slightly different numbers of 

 days. In figure 19, as well as in certain other graphs, the curves are 

 comparable in each case as to direction of slope; but it should be 



PIG. 20. Temperature efficiency summations for period of growth of special experiments. 



understood that the lengths of the ordinates are not in. all cases di- 

 rectly comparable ; the vertical scales employed are merely convenient 

 ones and are quite arbitrary. 



