i7, 6 Trelease: Salt Requirements of Wheat Plants 553 
The yield data of Table 4 are presented graphically in fig. 1 
(tops) and fig. 3 (roots) . On these diagrams areas of high yields 
(H) are marked with small crosses, and those of low yields (L) 
are marked with small circles. The highest value in each case 
is shown by a large cross, and the lowest, by a large circle. 
Water absoi-ption. — The total amount of water absorbed by 
each culture was obtained by adding together the partial quan- 
tities recorded at the several changes of the solution. The sums 
thus obtained (relative to the greatest one) are shown in the 
fourth column of Table 4. Following the method employed for 
dry-weight data, the cultures giving high and low values are 
indicated by the letters H and L, respectively. The highest 
water-absorption value is indicated by gothic type and the lowest 
by italics. 
Water requirement. — The amounts of water absorbed per unit 
of dry weight of tops and of roots were calculated for each 
culture. This ratio value is practically what has been termed the 
water requirement, and this term will be employed in this paper. 48 
The last two columns of Table 4 present these data. The letters 
H and L are employed as heretofore, the highest value being 
again indicated by gothic type and the lowest by italics. 
DISCUSSION OP SERIES I 
Appearance of plants. — As has been mentioned, the plants 
appeared greener in color with solutions having higher partial 
concentrations of magnesium sulphate, which suggests a direct 
relation between the color and the amount of magnesium present 
in the cells. Furthermore, the color was more intense in the 
cultures having low partial concentrations of potassium chloride, 
or in those cultures in which the other three salts were present 
in relatively large amounts. The cultures with high partial 
concentrations of potassium chloride may be considered as those 
in which the plants were deprived in a large measure of the 
essential elements, excepting potassium. 
Striping of the leaves occurred, as already described, with 
solutions having comparatively low potassium chloride values 
and very low monopotassium phosphate values. 
18 Briggs, L. and Shantz, H. L., The water-requirement of plants., II. 
A review of the literature, Bull. U. S. Dept. Agric., Bur. PI. Ind. (1913) 
285. Since practically all the water absorbed by such plants as those of 
the present experiments is given off by transpiration, the water-absorp- 
tion data represent total transpiration. 
