64 
WATER REQUIREMENT OF PLANTS. 
Table LIV. — Effect of dry and moist air on the water requirement of oats, 1 according to 
Heinrich (1894, pp. 170-171). 
Treatment. 
Dry mat- 
ter. 
Water. 
Water re- 
quirement 
on basis of 
dry matter. 
Moist air. 
Dry air.. 
Grams. 
5.444 
8.995 
Kilograms. 
0.6549 
5.5567 
*120 
618 
1 Duration of experiment, May 14 to July 29; 3 plants per pot. 
2 Heinrich gives 102, which is evidently an error. 
MONTGOMERY AND KIESSELBACH's EXPERIMENTS. 
The most conclusive experiments on this subject are those of Mont- 
gomery and Kiesselbach (1912) with corn. Two greenhouses were 
used, one of which was ventilated and the other kept as humid as pos- 
sible by wetting the floors and by using atomizers on the water system. 
The experiments were conducted in June and July. Apparently 4 
large, covered pots, each containing 2 corn plants, were used in each 
house. Self -registering thermometers and hygrometers were used to 
record the temperature and humidity in each house and the evapora- 
tion from a free water surface (36 square inches) was also measured. 
Montgomery and Kiesselbach's summary of the conditions in the 
two houses and the resulting water requirement is given in Table LV. 
Table LV. — Relation of humidity and other factors to the water requirement of corn, 
according to Montgomery and Kiesselbach (1912, p. 4). 
Dry 
Humid 
green- 
green- 
house. 
house. 
80 
75 
91 
88 
48 
72 
37 
58 
670. 36 
861. 77 
1,079 
1,070 
227. 785 
184. 230 
340 
191 
27.3 
19.2 
3,891 
2,187 
Ratio, 
humid 
to dry. 
Mean temperature: 
12 hours of night ° F. 
12 hours of day ° F . 
Mean relative humidity: 
12 hours of night per cent. 
12 hours of day do... 
Total weight of 8 plants grams. 
Average leaf area per plant square inches. 
Total water used kilograms. 
Water requirement: 
Based on dry weight grams. 
Based on square inches of leaf area do. . . 
Water evaporated from 36 square inches of free-water surface do. . . 
1.56 
1.70 
1.56 
Table LV shows that the corn grown in the dry house had a water 
requirement 56 per cent higher than that in the humid house. It 
is of special interest to note that the evaporation from a free water 
surface in the dry house exceeded that in the humid house by the 
same amount, 56 per cent. 
Another point of interest in connection with the above data 
which was not brought out by Montgomery and Kiesselbach arises 
285 
