290 BOTANICAL GAZETTE [APRIL 
Nine different stations were chosen, representing the range of 
habitats frequented by Tilia on clay soils. Stations F, G, and K 
are located on the old Lake Chicago plain, K being in Washington 
Park at Chicago, while F and G are located in an open forest on 
the flood plain of the Des Plaines River. These are environments 
having a strong prairie influence both as to environmental factors 
and flora composition. Station H is located in a mesophytic 
forest on a glacial upland in western Pennsylvania, where the chief 
components of the lower flora include such members as Adiantum, 
Actaea alba, Osmorrhiza, Botrychium virginianum, Aralia quin- 
quefolia, etc. Station I is near H, but occupies a position at the 
edge of an evergreen swamp which lies between glacial moraines. 
The soil here is of heavy blue clay overlaid by a few inches of rich 
humus. The undergrowth is composed largely of Taxus, Arisaema, 
Veratrum viride, and Symplocarpus. Station J is located at the 
foot of a steep east-facing embankment at the edge of a creek where 
the water content of the soil is always high and insulation is low. 
Station M is in a partially wooded rocky ravine where the chief 
members of the ground flora are Adiantun, Osmunda, Arisaema, 
etc. Station N is near the opening of the same ravine in a more 
exposed location on alluvial soil washed down from above by the 
stream. Station ZL is on the flood plain of the Neosho River in 
Kansas, and represents the species on the western prairie tension line. 
This series includes Tilia both in its normal environment, the 
mesophytic forest, and in abnormal ones when considered from an 
ecological standpoint. It also includes the species near the center 
of its distribution and on the limits of its range, where it is eliminated 
by members of another climax series, the prairie. Data have been 
presented in graph form to better illustrate such correlations as 
exist between the recorded factors. Graphs for all readings are not 
presented, because of the recurrence of very similar data at some of 
the stations. Those recorded, however, represent all the essential 
facts observed in the work at the various stations. 
' Normal features of transpiration curve 
It has been a commonly observed feature in work on foliar 
transpiration that the curve representing its index rises quite 
