VOLUME XLV 



> 



\ 



NUMBER 4 



Botanical Gazette 



APRIL 1908 



THE RELATION OF PLANT SOCIETIES TO 



EVAPORATION 



I 



Edgar N. Traxseau 



(with xine figures) 



During the summers of 1906 and 1907 the writer made a study of 

 the plant societies about Cold Spring Harbor, Long Island, N. Y. 

 In this connection an effort was made to obtain quantitative measure- 

 ii"^nts of the various environmental factors upon which depend habitat 

 differentiation and the succession of plant societies. The publication 

 of LmxGSTox's paper on "The relation of desert plants to soil mois- 

 ture and to evaporation'' in the autumn of 1906 suggested to me that 

 a series of vaporimeters, standardized and exposed in the various 



ant 



humidity 



Through the kindness of Dr. Livingston I was supplied with 

 several porous cups which were standardized with the vaporimeter at 

 A ucson. They were similar to those afterward sent out from the 

 Desert Laborator}- to various parts of the United States. For this 

 reason the readings given in this paper may be compared directly with 

 any obtained by other observers using these instruments. 



In the nature of the case, with the small number of instruments at 

 ray disposal, it became necessarv to establish one instrument as a 

 standard for the region. Because of the desirability of ha\ing a 

 ^cord of the rate of evaporation in the garden of the Station for 

 Experimental Evolution, the standard vaporimeter for my work was 

 placed in this sarden about ^^ east of the weather bureau instrument 



shelter. With 



mpared. WTien- 



as 



217 



