1922] THONE—STARVED ROCK 351 
mesophytic herbaceous flora, typified by Impatiens pallida, Pilea 
pumila, Campanula americana, and Lobelia syphilitica. Lianas 
were abundant, more so than at station 4. In general, this was by 
far the most mesophytic of all the stations. These three groups of 
stations were thus fairly typical of upland, slope, and bottomland 
respectively, and represented the principal plant associations reason- 
ably well. 
Instruments and methods 
An effort was made at each station to secure some measurement 
of each of the following physical factors: soil moisture, evaporating 
power of the air, intensity of solar radiation (in terms of its effect on 
evaporation from a free water surface), and temperature of soil and 
air. 
SoIL MOISTURE.—Soil moisture data were obtained by (1) the 
usual determination of the oven-dry weight percentage in samples 
of about 200 gm. each, compared with the wilting coefficients, as 
derived by the indirect method of Briccs and SHANTz; and (2) the 
“soil point”? method of Livincston and Koxetsv. All data were 
obtained for a level of approximately 7.5 cm. below the soil surface. 
This was the shallower of the two depths used by FULLER in his 
dune studies, and represents the level at which most seedlings begin 
their adventures. The soil points were used in sets of four, and 
results recorded as the average, to eliminate as far as possible the 
errors due to variability in instruments and soil. Holes were dug 
to the proper depth with a trowel, care being taken that none of 
them was within one-half meter of any hole in the same set or any 
previous set. As a rule, soil from the holes into which the points 
were set was taken for use in the moisture percentage determina- 
tions. From April 30 until July 1 it was possible to visit the 
stations only three or four times a month. From July 1 until 
September 20 determinations were made every forty-eight hours, 
except when rain intervened. - 
EVAPORATING POWER OF AIR AND SUNLIGHT INTENSITY.—Data 
on the evaporating power of the air and on the effect of direct solar 
radiation on evaporation rate were obtained by means of a pair 
of standard Livingston spherical atmometer cups at each station. 
