18 



In the case of com and wheat, more particularly the 

 latter, part of the '^ater recorded under the head of trans- 

 piration was removed from the plants "by guttation. 

 During their early period of growth drops of water were 

 often seen, in the morning, on the ends of the leaves of 

 those plants which were in the moist atmosphere. Toward 

 the latter part of the experiment this was not noticed. 



The results show very conclusively that transpiration 

 varies directly with the humidity of the atmosphere sur- 

 rounding the plants, hut growth, however, does not appear 

 to show a similar relationship to either of these factors, 

 in fact the largest total yield of dry matter in three 

 cases out of five was where the least quantity of water 

 was transpired. 



If grc^th were directly dependent upon transpiration, 

 as many of the leading plant physiologists assert, then 

 we would expect to find, for each species, a constant ratio 

 between the increase in substance and the water transpired 

 but such is not the case, as is shown in the last column 

 of Table III and by the results of experiments conducted 

 along this line by certain investigators. 



