74 



A MoNTAXK I; \IN-F()I!I>I . 



An examination of the curves in figure 5 will give a graphic concep- 

 tion of the comparative behavior of the five species in Set A, on three 

 in in-consecutive days, with progressively increasing evaporation. The 

 curves for the five plants are such as to reveal the dominant influence 

 of evaporation rate in controlling the transpiration. The water loss 

 of Asplenium alatum tended to exceed one-tenth of the evaporation, 

 area for area, throughout the three days, but exceeded it the least on 

 the day possessing the highest evaporation. Diplazium celtidifolium 

 ran considerably below one-tenth of the evaporation on the second day. 



2 40 



2.00 



1.60 



1.20 



.80 



-.40 



A.a. 

 D.c. 

 P.n. 

 P.t. 

 P.b. 



. 



10 



i i i r 



I i i : 



i i 



H A U. y 12 P It 



9 \ M n 1 P- M- 3 



6 A M 



Fig. 5. March of evaporation and of transpiration for five species during three days. The 

 species are: Asplenium alatum (A. a.), Diplazium celtidifolium (D. c.), Pilea nigrescens 

 (P. n.), Peperomia lurfosa (P. t.), and Peperomia basella folia (P. b.). Evaporation is 

 plotted at one-tenth its scale value. 



but parallel it closely on the third, indicating that it is capable of 

 withstanding an evaporation of 23 mg. per sq. cm. per hour the rate 

 at 12 noon on the third day without evidence of wilting. The three 

 species of lower transpiring rate than the ferns show a behavior in which 

 they sustain approximately the same relation to each other during the 

 three days, except for the tendency of the plants of lowest transpiring 

 power to exhibit a relatively more rapid rate of increase with increasing 

 evaporation. It is particularly true of Peperomia basellcefolia that its 

 rate of w r ater-loss gradually approaches that of Peperomia turfosa on 

 each of the successsive days. 



In the curves of figure 6 is exhibited the behavior of Set B of the 

 five species under discussion. The evaporation runs slightly lower in 

 this experiment than on the second day of the running of Set A, and 

 the transpiration of Diplazium and Asplenium outruns one-tenth of it. 

 The close correlation of the rates for all five of the plants with the rate 

 of evaporation is quite as marked as in the case of Set A. The relation 



