TRANSPIRATION BEHAVIOR OP RAIN-FOREST PLANTS. 103 



rates of relative transpiration, however, are not sharply reduced; in 

 fact they are either of the same order of magnitude as in other experi- 

 ments already commented on, or are even greater than in them (com- 

 pare tables 41, 42, and 43, showing rates at high humidities, with tables 

 23, 24, and 25). This is equivalent to saying that the degree to which 

 the conditions of high humidity cut down water loss from the plant is 

 equalled or exceeded by the rate at which they reduce the water loss 

 of the atmometer. I have already called attention to the correcting 



factor which must be introduced in comparing atmometric readings 

 taken in climates of distinctly unlike conditions of atmospheric humidity. 

 The differences in the character of the water films presented by the 

 atmometer under arid and under humid conditions would not be mani- 

 fested between atmospheric conditions as similar as those in my moist 

 chamber and those normally prevailing in the physiological laboratory 

 at Cinchona, or would, at least, be so small as to be negligible. 



