Relation of Xonavailable Water to Hygroscopic Coefficient 115 
hygroscopic coefficient and even to a point at which the milo had 
died. When conditions were favorable they adjusted themselves 
to the gradually increasing difficulty of absorbing water, due to 
the soil steadily becoming drier, by dropping their leaves one by 
one, transpiration finally almost ceasing. When, however, con- 
ditions causing an abnormally high transpiration suddenly set 
in, the plants died without dropping their leaves. 
Table 32. — Moisture conditions in cylinders carrying desert le- 
gumes. 
Depth of section 
Total water 
Free water 
I 
II 
III 
I 
II 
III 
Inches 
Per cent 
Per cent 
Per rent 
Per cent 
Per cent 
Per rent 
1-3 
2.6 
2.2 
2.2 
—3.0 
—3.4 
—3.4 
4-6 
2.8 
2.7 
3.0 
—2.8 
-2.9 
-2.6 
7-9 
3.6 
3.8 
4.0 
—2.0 
—1.8 
—1.6 
10-12 
4.3 
4.6 
4.4 
—1.3 
—1.0 
—1.2 
13-15 
4.8 
4.8 
5.1 
—0.8 
—0.8 
—0.5 
16-18 
4.9 
5.0 
5.2 
—0.7 
—0.6 
—0.4 
19-21 
4.9 
5.0 
5.3 
—0.7 
—0.6 
—0.3 
22-24 
4.8 
5.0 
5.2 
-0.8 
—0.6 
—0.4 
Black soil* 
5.7 
6.0 
5.3 
—5.6 
-5.3 
—6.0 
* This was between the 4th and the 9th inches and was entirely surrounded 
by H O Subsoil. 
The experiments furnish no evidence of any ability on the 
part of these legumes to utilize for growth the last portion of free 
water, but they indicate that this portion has a very high value 
for the maintenance of life and that even some of the water below 
the hygroscopic coefficient may be available for the maintenance 
of life in these plants. 
This evident ability of these desert plants to make use of 
water below the hygroscopic coefficient suggests that the absolute 
limit of soil water available for either growth or the mainte- 
nance of life may be the hygroscopicity as defined by Rodewald 
and Mitscherlich. 1 
THE HYGROSCOPIC COEFFICIENT VERSUS THE WILTING COEF- 
FICIENT IN COMPARISONS OF THE AVAILABLE 
MOISTURE OF SOILS. 
The free moisture in semiarid and arid soils, in so far as the 
above-described experiments and the results of unpublished field 
studies permit conclusions to be drawn, appears to be capable of 
more complete exhaustion by plant roots before the plants die 
1 Rodewald, H., and Mitscherlich, A. Die Bestimmung der Hygroskop- 
izitat. Landwirthschaftlichen Versuchs-Station, 1904, vol. 59, pp. 433-441. 
