Bouyoucos, Transpiration of Wheat Seedlings as Affected etc. 13 
ratio. Also as the density of the cell sap decreases, the degree 
or power of its physical properties to diminisli evaporation decreases, 
and therefore, the rapidity with which the water tends to go off 
rises proportionally. Thus, in either case, the amount of water 
lost increases directly with the reduction in concentration, and 
since the density of the cell sap diminishes with the increase in 
dilution of the outside solution, the increased transpiration per unit 
of growth as already noted, is probably the resnlt of the reduced 
intensity of the physical properties of both factors. 
The assumption made under the third factor, was tested ex- 
perimentally, and from all evidence it appears to be correct. This 
point was investigated by extracting the cell sap of the plants 
grown in the different concentrations of solution and determining 
its density. The extraction of the plant juice was performed by 
placing the green plants in a mortar, crnshing them with apestle 
tili the sap was pressed out, and washing ont the latter with 
distilled water. The pestling and washing were continued tili the 
plant juice had been taken out, and only the white über was left 
behind.* The later was then put in a piece of cheesecloth and 
rinsed several times in order to wash out every trace of the cell 
sap, and then pressed very firmly inside of the cloth to strain out 
all the solution. The extract was then filtered through ordinary 
fiter paper, its volume brought up to a definite point, and its 
density determined.' For the latter, two methods were used; 
1) the freezing point; and 2) the electrica! resistance, as determined 
by the Wheatstone bridge. A good deal of preliniinary work was 
done with both methods, and it was found that both gave exactly 
the same results, namely, that the density of the cell sap decreased 
with the diminution in concentration of the outside solution. Since 
the resistance method was the quicker and the simpler of the two, 
the majority of the final determinations were done by this method. 
While the resistance may not be as accurate or give as definite 
quantitative results as the freezing point, it shows, however, the 
comparative relation sought for. 
The plants used in this work were wheat. Beans were also 
used, but only in one case. Both kinds of plants were grown in 
solution cultures from about three to six weeks, and one kind also 
in sand cultures. 
In order that the density of the cell sap may be comparable 
among the different densities of solution, exactly the same weight 
of green plants grown in the various concentrations, was taken. 
Experiment I. This experiment consisted of growing wheat 
seedlings for 16 days in two different densities of solution, namely, 
4500 and 93.5 P. p. m. At the end of the above period they 
were harvested and exactly 3.9610 grams of green weight was 
taken, the cell sap was extracted by the method already described, 
diluted to 200 cc. with distilled water, and the density determined 
by both methods. The data obtained are given in the following 
tables. 
