i9o8] T RAX SEAU— PLANT SOCIETIES AND EVAPORATION 227 



J 



Station lo.— Upper beach on "Sand Spit" in Cold Spring Harbor, 

 1^°^ north of the Carnegie garden; altitude x^. The instrument was 



middle 



ph 



•P^ 



Cakile edentiila^ Asparagus officinalis, Euphorbia polygonijolia, Xan- 

 thium canadense, Cyperus Grayi, Polygonella articulata, and Ver- 



i thapsut 



aporation 



July 2-8 July 8-15 Total (13 days) 



cc 



138.2*=^ 251. 1 



Amt. evaporation, standard 131 -5 ^Si -9 283.4 



Comparative evaporation 85 . 8% 90 - 9% 88 . 6% 



It will be noted that at both Stations 9 and 10 the evaporation is 

 less than at the garden, in spite of the very xerophytic nature of the 

 vegetation. I was unable to analyze this result further with the 

 mstruments and time at my disposal It seems likely that the explana- 

 tion lies in the low rate of evaporation during the night, due to low 

 temperatures and increased humidity. They are more exposed to the 

 temperature effects produced by the cooler water brought in at the 

 now of the tides and are more subject to fogs. The correctness of 

 this suggestion can be tested only by an instrument which will record 

 at hourly interv^als. It is probable that the evaporation is higher on 

 the beaches during periods of bright sunshine. 



Station II, — -Salt marsh adjoining the garden of the Carnegie 

 Institution. The vaporimeter was set up near the outer end of the 

 middle line of the salt marsh (fig. 5). As this area is covered by water 

 at extreme spring tides, the instrument was necessarily raised about 

 5^"°^ above the ground. The jar was protected from the sun by a heavy 

 wrapping of felt paper. From the standpoint of the marsh vegetation 

 the instrument stood on the tension line between the Spartina poly- 

 stachya association and the zone dominated by S. patens. Other 

 plants occurring near this point are Atriplex hastata, A. aren^ria, 

 Tissa marina, Salicornia Bigelovii, Plantago maritima, and Limonium 



carolinianiim. 



Amt. 



June 14-23 Aa«. 5-12 Total (14 days) 



evaporation, Station 11 1 75 . 2^= 171 . 2« 346-4 



Amt evaporation, standard 141 -9 ^29. 7 2-;x.6 



Comparatiye evaporation . 123 . 4% X31 . 9^ X2 7 . 5^^ 



It is here then that the greatest evaporation rate for this \'icimt 



