626 
Journal of Agricultural Research 
Vol. V, No. 14 
occurred during the oat transpiration period. This may'account for 
the fact that the flattening of the transpiration curve of oats is not so 
marked as in the case of the other cereals. 
The wind velocity during these experiments was higher during the 
daytime than during the night hours. There is a fairly well-defined 
maximum between 7 and 10 o'clock and another secondary maximum 
in the afternoon. Wind-still periods seldom occurred. 
In Table XXXV are summarized the mean maximum values of the 
transpiration, evaporation, radiation, saturation deficit, and tempera¬ 
ture for each period; and the yield, time of harvest, and the period dur¬ 
ing which transpiration measurements were made. The range in mean 
wind velocity and the mean maximum transpiration, per gram of dry 
matter harvested have also been added to the table. 
A comparison of the data for the three varieties of wheat shows a 
close agreement. Kharkov produced the highest yield and transpired 
at the highest rate. Kubanka produced the least dry matter and trans¬ 
pired at the lowest rate. On the basis of dry matter produced Kharkov 
transpired most rapidly and Kubanka least rapidly. From a considera¬ 
tion of unpublished data on the transpiration of cereals from seed time 
to harvest, these observations appear to have been taken during the 
period of maximum transpiration for the crops considered. 
On the basis of transpiration throughout the total period of growth, the 
relative transpiration of Kharkov and Turkey wheat was the same—i. e., 
365 ±6 and 364 ±6 gm. of water, respectively, for each gram of dry 
matter produced. Kubanka transpired relatively more—i. e., 394±7 
gm. of water for each gram of dry matter. 
Oats transpired somewhat less rapidly than wheat in proportion to 
the amount of dry matter produced. A consideration of the tempera¬ 
ture data shows the mean maximum temperature for the oat period to 
be about 7 degrees lower than for the wheat period. This difference in, 
temperature and the resulting difference in humidity would be sufficient 
to account for the lower rate of transpiration of oats compared with 
wheat. On the basis of total transpiration, oats consumed 423 ±5 gm. 
of water for each gram of dry matter produced, or 7 per cent more than 
Kubanka wheat. 
Three different varieties of sorghum were used in the transpiration 
measurements—Minnesota Amber, milo, and Dwarf milo. The plants 
were apparently at the height of their transpiration during the measure¬ 
ments. The mean maximum transpiration rate of sorghum was higher 
in proportion to the dry matter harvested than for oats or wheat, but 
the physical conditions favored a more rapid transpiration during the 
sorghum period, as is shown by a comparison of the temperature, radia¬ 
tion, and saturation-deficit data. The slope of the sorghum transpira¬ 
tion curve near the peak is also much greater than for either wheat 
or oats. 
