1912] BRIGGS & SHANTZ—WILTING COEFFICIENT 21 
soil had been reduced to the point indicated in the last column of the 
table. The mean moisture content of the soil at the death point 
had been reduced to 85 per cent of the water content at the wilting 
point, while the mean soil moisture content at the end of the experi- 
ment was only 63 per cent of that at the wilting point. 
TABLE I 
THE WATER CONTENT OF THE SOIL IN SEALED POTS AT THE WILTING POINT AND 
DEATH POINT FOR KUBANKA WHEAT, AND AT A LATER PERIOD 
Pot no. Wilting point = ag Death point _— = Phe 
BSG aes 7.0 28 5.2 126 Eee 
Gee ce 7.9 25 5-9 126 2.6 
De ae 7.0 25 555 126 4.5 
orcas oc tne 6.6 19 6.4 126 4.9 
ee ae ye 27 5-9 134 4.8 
Yo. ee TiS 27 6.9 134 5-9 
ae ware 6.9 19 5-9 126 4-3 
RP ere Some. je 27 6.6 134 5.9 
eos ae 8.0 27 6.9 37 6.1 
TAs ce eit 7.3 27 6.2 134 4.9 
Mean. rae. 6.2 4.6 
The water remaining in the soil at the time the plant wilts can- 
not then with propriety be termed ‘“‘non-available.”’ We have 
shown that a considerable part of it is available, being absorbed 
by the roots of the dying or dead plant and evaporated from its 
aerial tissues, this process becoming slower and slower as the 
water content is reduced, and reaching its final limit in a condition 
of equilibrium between the soil and the air. 
It appears advisable, therefore, to use a more specific term for 
the moisture content of the soil corresponding to the wilting point 
of a plant, and we have employed the term “wilting coefficient” in 
this sense in the present paper. The wilting coefficient is defined 
then as the percentage water content of a soil when the plants 
growing in that soil are first reduced to a wilted condition from 
which they cannot recover in an approximately saturated atmos- 
phere without the addition of water to the soil. 
The method used in determining the wilting coefficient has been 
