1921] CRIBBS—TILIA AMERICANA 299 
to be similar to the average rate for the clay positions, where the 
growth water percentage is relatively high. The average transpi- 
ration rate for the mesophytic clays is approximately one-half that 
exhibited on the open sands. The growth water in the mesophytic 
forest, despite the lower transpiration rate there, is on the average 
at least six times as great as on the dunes. 
Reference to data for stations located on clay shows that the 
growth water for these positions fluctuates about 18 per cent, 
W 
Transpiration  T. 
srrseeeseee Soil tempevature 5S: 157.68 . 
w———- Growth Water EW. ‘ 
, 
i - 
eS 6. 2 A Oe ee ee 
Fic. 7.—Data for soil temperatures, growth water, and transpiration as recorded 
at all stations on sand and clay; note high transpiration associated with low growth 
water and high soil temperatures. 
being above more often than below this average. Notwithstanding 
the fact that growth water is always relatively abundant, the tran- 
spiring ability is proportionately low, with but two exceptions not 
exceeding o.5 at any time during the investigations. The close 
approximation of the average transpiration rate on the mesopbytic 
clay soils to that of stations A and B in the dune forest is also 
evident in fig. 7. Thus the comparative equality in the transpiring 
power, while the growth water ranges from an average of wid eal 
cent at station A to 157.68 per cent at station I, strongly indicates 
