exists between the amount of dry matter elaborated and 

 the weight of water transpired by the plants during vegeta- 

 tion. This view is also held by Lawes and Gilbert (7). 



Green (4), in addition to the view that transpiration 

 is necessary in order that the leaves may be supplied with 

 inorganic salts, maintains that it is imperative in order 

 to prevent a rise of temperature to a point which would be 

 fatal to the plant. He states that the amoimt of radiant 

 energy talcen up by the leaves has been computed to be near^ 

 ly 50 times the amount which can be utilized in the process 

 of photosynthesis ; if the heat were allowed to accumulate 

 in the leaf uncheclced it has been calculated that its tem- 

 perature would rise during bright sunshine more than 12 

 C. per minute. Pfeffer (9) and Tschaplowitz (IS) also 

 recognize the probability of a regulatory influence of 

 transpiration upon the temperature of the plant. 



Kreusler (6, See T'oods, 15), does not regard the check- 

 ing of transpiration by a complete saturation of the at- 

 mosphere as unfavorable to assimilation but, on the other 

 hand, holds that assimilation may be reduced by a dry at- 

 mosphere, which is conducive to excessive transpiration, 

 long before the turgescence of the leaf is visibly diminished, 



