602 
Journal of Agricultural Research 
Vol, V, No. 14 
in figure 5, that sorghum, even under the more severe conditions 
imposed, gave no indication of a flattening of the peak of the transpira¬ 
tion curve. Furthermore, the maximum of the sorghum transpiration 
curve occurs at approximately noon, and the curve is nearly symmetrical. 
In brief, the transpiration graph of sorghum appears to follow more 
nearly the radiation curve than either wheat or oats. It is of interest 
in this connection to note that sorghum is one of the most efficient of the 
crop plants in the use of water, the sorghum varieties used in these exper¬ 
iments having a water requirement amounting to only 64 per cent of 
that of the oat plants. 1 
RYE 
The transpiration data for rye (Secale cereale ) 2 on clear days are given 
in Table XV. These observations were made outside the inclosure, 
under freely exposed conditions, from June 22 to July 3, 1914. The 
environmental measurements for this period are given in Tables XVI to 
XX, inclusive. Hourly evaporation measurements from a free-water 
surface were also made in 1914, with the aid of an automatic balance. 
The hourly means for the environmental factors are plotted in figure 6, 
together with the hourly evaporation and the hourly transpiration of 
rye, the latter being represented by the mean of 12 automatic records 
taken on six different days. 
1 Based upon water-requirement measurements of the same plants. (Briggs and Shantz, 1914.) 
* Spring rye, C. I. No. 73. 
