126 



WILLIAM H. BROWN 



water content at the time of wilting and the evaporation rate 

 for the preceding hour. The highest soil moisture content (ex- , 

 periment 1) occurred in the case of a plant wilting in the open, 

 with the highest evaporating power of the air; and the lowest 

 percentage of soil moisture (experiment 16) was obtained in case 

 of a plant wilting in the moist chamber. It is to be noted espe- 

 cially that an evaporation rate of somewhat over 7 cc. per hour 

 invoked wilting with two or three times as much water still in 



TABLE 2 



Percentage of soil moisture, at the time of wilting of similar plants of Martynia under 



different evaporation conditions 



the soil as was present when wilting was brought about under 

 an evaporation rate of less than 1 cc. per hour. 



Another kind of experiment was carried out. Three plants 

 which had wilted under a high rate of evaporation were trans- 

 ferred to a position with a lower rate. Here they revived quickly 

 without addition of water to the soil. They were then allowed to 

 wilt in the new situation, which they did with considerably less 

 water in the soil then in the first case. The results are given 



