302 BOTANICAL GAZETTE [APRIL 
cells, thus affecting the diffusion gradient and resulting in a greater 
water loss. 
Comparison of swamp and upland mesophytic types 
As previously stated, station H is located in a typical upland 
mesophytic forest on mixed morainic clay, and station J is located 
on the border of a swamp where the undergrowth is composed 
largely of Taxus and spring perennials, and where the tree stand 
pai a 
Dae, “< 
z0 fr ie SS 
7 eis ig 
2 oe ie fi fs, 
, vd ae i ibe. 
pe Be 
Te a 
i 
\ | | 
\j 
\\ AN 
Ay 
jo 
. 8.—Relative humidity, evaporation, and ee for stations H and J, 
setae average of 5 days’ readings at each statio 
includes Tsuga, Fraxinus, and Acer. Beneath the humus at 
station I is a heavy blue clay soil which is saturated during practi- 
cally the entire growing season, and Tilia, as do most other forms of 
vegetation in similar situations, grows to form a low broad hum- 
mock, because the roots, being unable to penetrate deeply, spread 
out on the surface. In this supersaturated environment a peculiar 
behavior was observed in the transpiration stream. ‘This is shown 
in fig. 8, which is a composite graph, each curve representing the 
average of five separate days’ readings and including relative hu- 
midity, evaporation, and transpiration. It will be noticed that both 
