Journal of Agricultural Research 
Vol. VII, No. 4 
I98 
The results obtained in case of alfalfa are of special interest, for the 
plants were much more advanced than those just considered. In fact, in 
two of the three alfalfa measurements given the periods were terminated 
by the harvesting of the plants while in full bloom. The data show that 
during the periods considered the transpiration coefficient of alfalfa was 
compounding at the rate of 8 to 9 per cent per day, thus doubling in value 
every 8 or 9 days. 
-A 5 
- A* 
-A 2 
-A O 
• 2.6 
• 2.6 
• 2.4 
- 2.2 
• 2 . 0 , . . 
t6 20 22 24 26 26 20 2 4 6 6 /O /2 /4 /6 
xJU/V£ /S/4 'JUl*' 
Fig. is. —Graph showing a linear relation between the logarithm of the transpiration-evaporation ratio 
of Algeria corn and the time. 
Table XX .—Rate of increase in the transpiration coefficient of different crops in IQ14 
Crop. 
Observation period. 
(a) 
Daily rate 
of increase. 
Days re¬ 
quired for 
k to double 
in value. 
Com, Northwestern Dent. 
Corn, Algeria. 
June 18-July 9. 
June 18-July 11 
O. 026 
.044 
Per cent. 
6. 2 
10. 7 
11. 6 
6.8 
Sorghum, Minnesota Amber. 
June 18-July 9- 
. 041 
9.9 
7-3 
Sudan grass (in inclosure). 
June 18-July 10- 
.066 
16. 4 
4. 6 
Sudan grass (in open). 
June 24-July 11- 
. 082 
20. 8 
3 * 7 
Alfalfa, E23 (first crop in open). 
June 16-July 10.... 
•033 
7-9 
9. 1 
Alfalfa, E23-20-52 (first crop). 
June 19-July 9. .. 
•°37 
8.9 
8. 1 
Alfalfa, E23-20-52 (second crop).... 
July 18-Aug. 5.... 
•037 
. 8.9 
8. 1 
A test of the validity of the computations may be obtained by com¬ 
paring the observed graph of the transpiration coefficient with that com¬ 
puted from equation (3). The result of such a computation in the case 
of Sudan grass (in the open) is given in figure 16, the computed graph 
being represented by the smooth curve, while the observed values are 
represented by circles. 
