RESISTANCE BY LEAVES TO WATER LOSS 



17 



dition for the hour. From table 2 it is found that this range 

 is 0.80 to 5.24, or 1.0 to 6.6. The different values obtained for 

 the range of transpiring power in the plants of experiment I, 

 may be summarized as follows: 



Range of relative lrunspiratio7i ratio for Physalis 



By white atmometer 



Plant 1 1 to 6.7 



Plant 2 1 to 5.9 



Average 1 to* 6. 3 



By brown atmometer 



Plant 1 1 to 6.4 



Plant 2 1 to 4.8 



.■\verage 1 to 5.6 



Range of index of transpiring power 



By paper test 1 to 6.6 



It is evident that the result arrived at by means of the cobalt 

 chloride paper is in very satisfactory agreement with those derived 

 by the indirect methods. 



To compare the different series, in regard to the manner of 

 occurrence of the variations which they indicate, graphs have 

 been prepared for each series. The two graphs of relative tran- 

 spiration for one plant are so nearly identical with those for the 

 other, that the graphs for plant 1 alone are given here. 



Figure 1 presents the graphs of the relative transpiration of 

 plant 1, by the white and by the brown instrument, the graph of 

 the transpiring power of the leaves as a whole (by hygrometric 

 paper), that of absolute transpiration of plant 1 and that of evap- 

 oration from each of the two atmometers. All of the graphs are 

 comparable throughout, being constructed to pass through a 

 common point at hour 1. The abscissae represent hourly inter- 

 vals and the ordinates are taken directly from tables 1 and 2. 

 Dawn occurred this day at about 3 hours 30 minutes, sunrise 

 at 6 hours. The forenoon was partly cloudy, as is clearly shown 

 by the behavior of the atmometers. There was very little wind 



THE PL.VNT WORLD, VOL. 16, NO. 1, JANUARY, 1913 



