140 Nebraska Agricultural Exp. Station, Research Bui. 6. 
14 per cent. The water used per gram dry weight of ear was 
reduced 4.3 per cent, per gram total dry matter 7.9 per cent, 
and per square inch leaf-area 28.2 per cent. The ratio of leaf- 
area to dry matter was 40.4 per cent greater and the ratio of 
weight of ear to weight of stalk was 11.2 per cent greater in the 
deficient moisture content than in the optimum. The height of 
plants also was reduced 26 inches, or 25 per cent. 
At first thought it would appear that a greater efficiency in 
the use of water had been effected by a reduction of the soil 
moisture below the optimum. However, a saving of 7.9 per cent 
in the water requirement per unit total dry matter, and 4.3 per 
cent in the water requirement per unit weight of ear, was accom- 
plished only thru a reduction of 30.7 per cent in the yield of dry 
matter and 28.5 per cent in the weight of ears. Consequently, 
a reduction of soil-moisture content below the optimum would 
not be practicable in order to bring about a saving in the water 
requirement per unit dry matter. 
It is clear that the efficiency of the leaves in elaborating dry 
matter is reduced with a deficiency of soil moisture, the average 
increase in leaf-area per unit dry matter being 40 per cent in 
these experiments. This is probably due to a relatively more 
normal growth up to the time of full leaf development, followed 
by a retardation of growth caused by excessive evaporation 
demands occurring during August and the latter half of July. 
The reduction of 28.2 per cent in the water loss per unit leaf- 
area would perhaps appear to support the old theory that the 
leaf stomata exert a regulative control by partial closing when a 
deficiency of soil moisture exists. However, it must be borne in 
mind that these plants were doubtless less exposed to evaporation 
influences, being 26 inches less in height. The free-water-surface 
evaporation data in Table 50, page 123, show an average reduction 
of 17 per cent in the evaporation rate with an average reduc- 
tion of 23 inches in elevation in a cornfield from 84 inches to 61 inches. 
During the two years 1910 and 1913, the plants also grew slowly 
and the maximum leaf development did not occur until some- 
what later than with the optimum soil moisture. This reduced the 
length of time during which the total leaf -area evaporated water, 
and thus reduced slightly the relative water loss per square inch 
leaf-area. The close correlation between the hourly and daily 
transpiration and evaporation rates in relation to climatic factors 
shown earlier in this bulletin also fails to support the theory of 
stomatic control. If there was an inherent reduction in the 
transpiration rate per unit leaf-area aside from the influences 
mentioned above, it was perhaps due to a lower water content 
or lessened turgidity of the leaves. It is a principle in physics 
