154 
Journal of Agricultural Research 
Vol. XIV, No. A 
solution and another to TottinghanTs best solution for wheat tops, 
each with a total concentration value equal to that of the 3-salt solu¬ 
tions. Thus, the actual tests of the effects of the 36 different salt com¬ 
binations upon the growth of the plants in this series, were not begun 
until the plants had passed through the first physiological growth period 
extending from the germination of the seed to the flowering stage. The 
cultures were now continued, with renewal of solutions as before, until 
the seeds were mature. This required 28 days. The entire active 
growth period of the plants of this series extended, therefore, over an 
interval of 52 days after the seedlings had been transferred to the culture 
vessels. The series was then repeated. The second series was carried 
out in the same manner as the first, but under somewhat different seasonal 
conditions. 
In order that all the plants might be exposed to somewhat similar 
changes of temperature, light, and moisture, the cultures were arranged 
in rows on a central table in the greenhouse, in such a manner as to avoid, 
as far as possible, unequal shading of one culture by another. Through¬ 
out the growth period the cultures were shifted in position at regular 
intervals, in accordance with a definite plan. 
As previously stated, the culture solutions were renewed at intervals 
of four or five days. At the time of each renewal of solutions, the 
absorption (and approximately the transpirational water loss) was 
determined by measuring the volume of the used solution before dis¬ 
carding it, and subtracting this volume from the original volume (515 cc). 
The total transpirational water loss for each culture was obtained by 
summing the losses for the partial periods between each two successive 
changes of solution. 
At the end of the growth period, after practically all the seeds were 
ripe, the plants were harvested. The tops were separated from the 
roots just above the topmost lateral root. The seeds were carefully 
removed from the tops, and the three portions were separately dried 
to constant weight at a temperature of about 103° C. The dry weights 
were then obtained. 
Records were kept of the temperature in the greenhouse where the 
culture series were conducted. Daily maximum and minimum tem¬ 
perature readings were obtained from thermometers protected from 
direct sunlight. The moisture conditions of the atmosphere throughout 
the growth periods were indicated by means of the evaporation rates 
from spherical porous-cup atmometers. Several of these instruments 
were placed among the cultures on the greenhouse table, and daily read¬ 
ings were taken. These were corrected to the Livingston (2) standard 
spherical atmometer. 
EXPERIMENTAL RESULTS 
The first of the two culture series carried out during the later develop¬ 
mental growth period (between the flowering stage and the ripening of 
