234 BOTANICAL GAZETTE [MARCH 
the plant wilts, the soil farthest from the roots contains more 
water than the soil immediately surrounding the roots. Conse- 
quently, the determination of the moisture content of the whole 
soil mass at the time of wilting gives too high a value for the wilting 
coefficient. Aside from the Colocasia, a variety of corn gave the 
highest relative wilting coefficient, namely, 1.06. The several 
varieties of corn differed slightly, the lowest value being given by 
Boone County white, a variety native to wet regions. Mexican 
and Indian varieties, natives of dry regions, gave no evidence of 
being able to reduce the soil moisture content lower than other 
varieties. Only slight differences were found in the relative wilting 
coefficient in the different varieties of sorghum, a crop extensively 
grown in semi-arid regions. The relative wilting coefficient of two 
of the varieties tested was 0.94, indicating that these varieties 
were capable of reducing the moisture content of the soil somewhat 
below the point reached by corn at the time of. wilting. The 
difference in the wilting coefficient of the varieties of the small- 
grain crops, millet, wheat, oats, and barley, is slight, the extreme 
range for the four crops being from 0.95 to 1.03. The value of the 
wilting coefficient obtained for rye was 0.94 and for Japan rice 
0.92. The low value found for the latter plant is of special interest 
in view of the fact that it is generally considered necessary to keep 
rice fields flooded during the greater part of the growing season. 
The different grasses, most of which are natives of the Great 
Plains of the United States, gave ratios differing only slightly from 
each other and from the small grains. Most of the legumes, on the 
other hand, and certain of the coarse-rooted plants of the Great 
Plains, gave slightly higher values for the relative wilting coefficient. 
These high values, we believe, are to be attributed to imperfect 
root distribution rather than to any inherent inability of these 
plants to reduce the soil moisture content to the point reached 
by other plants. 
The miscellaneous plants upon which only a few determinations 
have been made are grouped in the last part of the table as hydro- 
phytes, mesophytes, and xerophytes. The water plants gave a 
_ mean wilting coefficient slightly higher than the other groups, due 
to the presence in this group of Isoetes, submerged plants of which 
