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 abundant. 
However, Tschaplowitz, 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 produce a pound of dry matter 
when the soil is fertilized than when it is not ferti- 
lized. Moreover, he observed that the enriching of 
