304 BOTANICAL GAZETTE [APRIL 
The curve for July 16 shows that it is characterized by a late morn- 
ing rise, a feature quite unusual for the dune series. In addition, 
the maximum is reached at 1:00 P.M., when the usual occurrence 
in this environment was a depression at that hour. There was also 
a high transpiration recorded during the afternoon without the 
appearance of a secondary mode at 4:00 to 5:00 P.M. 
The first of these features, the late morning rise, is attributed to 
the atmospheric conditions, which show a very low temperature 
1 Seas 
6:00 700—=—« 00 100 sCse:s=‘ivSOSSCSOS*“‘“ OS SO OST 
Fic. 9.—Record of readings at station C for July 16, 21, and August 26, showing 
3 distinct ae of curves although records were taken from same leaves. 
(about 17°), but especially a low evaporation rate and a high relative 
humidity. The general weather conditions show a cloudy period, 
following precipitation from about 5:00 to 6:20 A.M. At 10:00 
A.M. the weather became clear, followed by a slight increase in 
temperature, evaporation, and saturation deficit of the air. Not- 
withstanding the slow increase in these factors, the foliar tran- 
spiration was found to increase much more rapidly in proportion. 
Thus the maximum transpiration index was greater than was 
observed to occur under similar conditions on the clays, except 
