194 
Journal of Agricultural Research 
Vol. VII, No. 4 
leaved plants lost water almost as rapidly as the older plants on which 
the lower leaves either drop off or become relatively inactive. 
Four sets of alfalfa were included in these measurements. Three of 
these sets were grown from seed, while the fourth alfalfa, 162-98A, was 
grown from cuttings. The transpiration coefficient of the latter was 
already 25 per cent of the maximum when the measurements were begun. 
Some of the plants in the fir§t crop began to bloom when the transpira¬ 
tion coefficient was only 40 per cent of the maximum. In the second 
and third crop's the plants were harvested shortly after they had developed 
flowers. The march of the transpiration coefficient for each variety was 
approximately the same, with the exception of the first crop of alfalfa, 
163-98A, which developed much more rapidly than the other varieties. 
The set in the open developed more slowly than in the inclosure. 
The relative loss of water at different periods in the growth of a crop, 
the evaporation rate being uniform, can readily be determined from 
the graphs representing the transpiration-evaporation ratio. The 
weekly loss from different crops expressed in percentages of the total is 
given in Table XVIII. 
Table XVIII .—Weekly transpiration under uniform conditions of evaporation expressed 
in terms of percentage of the total , IQ 14 
Crop. 
1st. 
2d. 
3 d* 
4th. 
5th. 
6th. 
7 th. 
8th. 
9th. 
10th. 
nth. 
Northwestern Dent com. 
2 
A 
IO 
T *2 
TA 
Algeria corn. 
2 
A 
8 
22 
A 4 
TA 
*4 
t e 
*3 
13 
11 
7 
8 
Sorghum, Minnesota Amber.. 
2 
•r 
5 
11 
14 
T A 
12 
T 2 
11 
Sorghum. Dakota Amber. 
2 
e 
10 
T A 
T C 
2 2 
7 
Sudan grass (first crop). 
1 
0 
2 
8 
17 
A 4 
17 
1 J 
28 
Ip 
11 
16 
10 
7 
Sudan grass (first crop in open) .. 
1 
I 
6 
17 
17 
20 
20 
18 
Alfalfa, E23-20-52 (second crop).. 
2 
10 
22 
30 
36 
Alfalfa, E23 (second crop). 
3 
10 
21 
30 
36 
Alfalfa, E23 (second crop in open) 
2 
11 
23 
32 
32 
Alfalfa, 162-98A (second crop).... 
4 
13 
23 
30 
3 ° 
The loss from com and sorghum during the week preceding the meas¬ 
urements was very slight, amounting to less than 1 per cent of the total. 
The mean transpiration of the four crops for the second and succeeding 
weeks was 2, 5, 10, 14, 13, 15, 14, 12, 11, and 7 per cent of the total. The 
drop in the sixth week is not significant and is probably due to imperfect 
measurements of transpiration during days when rain occurred. 
Sudan grass in its early stages of growth developed more rapidly in the 
inclosure than in the open. Alfalfa produced its second crop in a period 
of five weeks, two-thirds of the total transpiration occurring during the 
last two weeks of the growth period. The transpiration coefficient 
changed very rapidly, being approximately one-third the maximum in 
the second week and two-thirds the maximum in the third week. 
