42 



WATER-RELATION BETWEEN PLANT AND SOIL. 



TRANSPIRING POWER (T-^E). 



The February graph of this feature shows its maximum (2.98) with 

 hour 14, the same hour as occurs the maximum of absolute transpiration. 

 The period of low night values extends from hour 17 to hour 6, its aver- 



FiG. 3. — Graphs for Pelargonium. 



age value being 0.42 and the ratio of the maximum to this being 7.1. 

 The March graph exhibits its maximum (2.19) with hour 12, also at the 

 same hour as occurs the maximum for absolute transpiration. The 

 March night period extends from hour 16 to hour 6, with an average 

 value of 0.27. The maximum is 8. 1 times this average. This March graph 

 bears evidence of some incipient drying of the leaves about noon, 

 thus agreeing with the corresponding graph of absolute transpiration. 



