1919] CRIBBS—TILIA AMERICANA 269 



humidity, wind, light, temperature, etc., might influence the rate 

 of transpiration in the field, and to compare its relative influence 

 in the different environments. In each instance readings were 

 taken at stations A, B, and C on the same day. The same may 

 be said for stations D and E. Fig. 7 represents the records of 

 relative transpiring power, temperature, relative humidity, and 

 evaporation for A, B, and C on July 21, 19 18. As in the following 

 graphs, the scale to the left is for the index of foliar transpiring 



Tra n sp i rat ion — — 



Evaporation — 



Temperature ____ 



Relative Humidity—...— 



u 



lu 

 la 

 la 

 ±a 



SToo fcloo 7IQQ Hoc g\oo IOI00 1/Iqj u| L j ;|,)j j\oo j| 0L , Bigg J l ot) till WW " 



Fig. 7. — Graph giving transpiration, temperature, evaporation, and relative 

 humidity curves of stations A, B, and C for July 21, 1918; scale similar in all follow- 

 ing graphs (see text). 



power; the inner one to the left is for relative humidity; the 

 inner one to the right is for evaporating power of the air and is 

 expressed in cubic centimeters per hour ; and the scale to the right 

 records the atmospheric temperature in degrees centigrade. Time 

 is indicated at the bottom of each graph. 



It will be noted that there is a close parallelism between the 

 curves representing temperature, evaporation, and relative humid- 

 ity. This is in fact what would be expected, as these factors are 



