1914] HASSELBRING—EFFECT OF SHADING 275 
proper state of moisture was restored by adding measured quantities 
of water at the surface, the controls being treated in the same way. 
In all, five liters of water were thus added from November 27 to 
January 14. 
From the time that the tanks were placed in the field, the loss 
of water from the soil and plants was determined by daily weighings. 
For these weighings a small platform scale specially constructed 
for the purpose was used. This scale was equipped with agate 
bearings and with two riders which could be clamped at any point 
on the beams, one of which was graduated in units of one gram for 
the smaller rider. The end of the beam was provided with a 
pointer which indicated the position of exact balance. The scale 
Was sensitive to one gram with the load of 35 kilograms, approxi- 
mately the weight of the tanks when filled. It was placed per- 
manently on a low solid platform in a shelter to which the tanks 
could be conveniently brought. The water lost from the soil and 
plants was replaced each day by the addition of enough water 
through the inlet tubes to bring the tanks up to the standard 
weight. While the plants were small, the quantity of water thus 
added was measured from a burette, but later, when the daily tran- 
spiration was large, the bulk of the water required was added by 
means of graduated flasks marked for pouring, only the final frac- 
Hons being run in from the burette. The operation was begun at 
4:00 P.M. each day and required about two hours for its comple- 
tion. The quantity of water thus added was recorded as the daily 
loss by transpiration from the plants and evaporation from the soil. 
For obtaining the total transpiration of the plants, the average 
quantity lost from the three control tanks was subtracted from the 
total quantity lost from each of the other tanks in the same station, 
the loss from the controls being regarued as representing the quan- 
ty lost from the soil of the tanks containing plants. The differ- 
ence caused by the partial shading of the soil of the planted tanks 
had to be disregarded. 
The plants were harvested on January 28, at about the time of 
maturity of the general crop. At that time the leaves were fully 
Srown and the inflorescence was well developed, a few flowers 
having opened. 
~ ‘i, 
