AMOUNT OF TRANSPIRATION 183 



rapidly than those that evaporate less ? These ques- 

 tions arose very early in the period characterized by 

 an active study of transpiration. If varying the 

 transpiration varies the growth, there would be no 

 special advantage in reducing the transpiration. 

 From an economic point of view the important ques- 

 tion is this : Does the plant when its rate of transpira- 

 tion is reduced still grow with the same vigor? If 

 that be the case, then every effort should be made by 

 the farmer to control and to diminish the rate of 

 transpiration. 



One of the very earliest experiments on transpira- 

 tion, conducted by Woodward in 1699, showed that 

 it required less water to produce a pound of dry 

 matter if the soil solution were of the proper concen- 

 tration and contained the elements necessary for 

 plant growth. Little more was done to answer the 

 above questions for over one hundred and fifty years. 

 Perhaps the question was not even asked during this 

 period, for scientific agriculture was just coming into 

 being in countries where the rainfall was al)undant. 

 However, Tschapl(jwitz, in 1878, investigated the 

 subject and found that the increase in dry matter is 

 greatest when the transpiration is the smallest. 

 Sorauer, in researches conducted from 1880 to 1882, 

 determined with almost absolute certainty that less 

 water is required to j^roduce a pound of dry matter 

 when the soil is fertilized than when it is not ferti- 

 lized. Moreover, he observed that the enriching of 



