192 
Journal of Agricultural Research 
Vol. VII, No. 4 
The transpiration coefficient of Kubanka wheat had reached half the 
maximum value when the daily weighings were begun, although the 
total transpiration from seedtime to this date was only io per cent of 
that for the whole season. A gradual increase in the transpiration coef¬ 
ficient is recorded from June 16 to a maximum on July 12. Although 
the plants began to head on June 15, this produced no marked change 
in the transpiration coefficient. The drop in the graph following the 
period of heading is not significant in this connection since a similar drop 
was recorded for the other crops, and it is evidently due to the failure of 
Fig. 9.—The ratio of daily transpiration of different crops grown 4 n 1915 to daily evaporation (shallow 
tank) plotted in percentage of the maximum. 5 signifies that the plants were forming shoots; H, 
heading; F, flowering; and D, lower leaves dying. 
evaporation and transpiration to respond proportionately to the weather 
conditions on these days. The gradual decrease in the transpiration 
coefficient following the maximum is indicated by the graph and begins 
almost one month before harvest. At harvest time the transpiration 
coefficient of Kubanka was still 20 per cent of the maximum. 
Galgalos wheat which began to head two days later than Kubanka 
reached its maximum four days earlier. The period of gradual decline 
was approximately one month long and the transpiration coefficient at 
harvest was 20 per cent of the maximum. The depression in the curve 
in the early part of the period of decline is probably not significant since 
