ECOLOGY OF TILIA AMERICANA 
II. COMPARATIVE STUDIES OF THE FOLIAR 
TRANSPIRING POWER 
JAMES E. CrIBBs 
(WITH TEN FIGURES) 
A comparative study of the foliar transpiring power of Tilia 
as recorded in the field for dune environments (1) preceded this 
work, which is an extension of the former investigations, and is 
concerned with the data recorded for the same species as obtained 
from a wide range of habitats on clay soils. 
The methods employed were ‘essentially the same as described 
in the former discussion of the dune series. A 3 per cent cobalt 
chloride standard paper was used in all the work for determining 
the relative transpiring power, and was applied by means of the 
clip devised by Livincston (4). As in the former experiments, 
readings were taken on two leaves at each station, the same leaves 
being employed in subsequent readings. Records were taken at 
approximately hourly intervals, and as recorded represent the 
average of four to six readings. Curves are plotted for both leaves. 
The slight difference observed in the readings for the two leaves, 
which occasionally became considerable, was in most instances 
attributed to the relative maturity and specialization of the epi- 
dermis and cuticle. 
Measurements of the chief environmental factors were recorded, 
and special features of the environment taken into consideration. 
‘The chief factors measured were evaporation, relative humidity, 
atmospheric temperature, soil temperature, wilting coefficient, 
and growth water. The occurrence of alternate sun and shade, 
velocity of the wind, fog, and passing thunder showers were special 
features which were found to bear a definite relation to the oscillat- 
ing behavior of the transpiration stream. Measurement and com- 
putation of these factors were carried out in the same manner as in 
the preceding experiments. 
289] [Botanical Gazette, vol. 71 
