66 BROOKLYN BOTANIC GARDEN MEMOIRS 



Cherry Grove, on Fire Island Beach 131 1-4 cc. = 89.8% 



Coram, in center of Long Island 1234.2 cc. = 84.5% 



Crystal Brook is in the center of a heavy oak forest and the open station 

 there was selected because it was sheltered from the drying southwest wind 

 of summer. Coram is in the pitch pine region and exposed to this wind, 

 while Cherry Grove is out on the barrier beach, and in full exposure to the 

 winds from the sea. And yet the figures are all within 16% of one another, 

 so that while the conditions of Montauk, judging by the vegetation, are 

 totally different from the other localities, this lack of forest growth, in so 

 far as it is due to wind, is certainly not expressed by the readings of the 

 white atmometers. While the evaporation is higher than for anywhere else 

 on Long Island, it is not so much higher as the vastly different vegetative 

 condition of the Point would suggest it should be. 



The accompanying graph (Fig. 23) shows by unbroken and broken 

 lines the details of how the white atmometers in the open at Montauk 

 differed from the other Long Island stations in the open, which have been 

 taken at Coram, Crystal Brook and Cherry Grove and averaged. 



Black atmometers were exposed in all the stations, two feet from the 

 white instruments, and appear from the readings to be a more sensitive 

 and perhaps better indicator than the white ones. While neither the white 

 nor black atmometers profess to be an accurate measure of transpiration, 

 the curve of either or of their difference (so called solar radiation) has a 

 very general correspondence to the transpiration of twelve trees as shown 

 by Bates.* To that extent at least the Livingston atmometers, while not a 

 measure of transpiration are a pretty good indicator of its variation over 

 longer or shorter periods, and in average conditions of growth where wind 

 velocity is more normal. In fact, Burns has shownf that "Evaporation- 

 transpiration coefficients based on unit of dry weight . . . show that re- 

 sponse of the plants agree more closely with the black atmometer than with 

 the white atmometer." The curves in the paper by Bates, already referred 

 to, also show greater correspondence between the Livingston black at- 

 mometer and transpiration, than with any other type of evaporimeter 

 with which he experimented, except the all-metal device which he describes 

 there. 



In the light of the statements of Burns and Bates the evaporation from 

 the black instruments at Montauk during the four day period July 25-28 



* Bates, C. G. A new evaporimeter for use in forest studies. Monthly Weather 

 Review 47: 283-294. 1919. 



t Burns, G. P. & Hooker, F. P. Studies in tolerance of New England trees II. Re- 

 lation of shade to evaporation and transpiration in nursery beds. Bull. Vermont Agr. 

 Exp. Sta. 181 : 235-262. 1914. 



