Bovit: NON-AVAILABLE WATER IN SOILS 287 
form of water which land plants use for a large part of their lives. 
The uniformity in the above results testifies to the smallness of 
experimental errors in sampling, weighing, et cetera. 
The amount of non-available water was not determined in the 
0.8 per cent. set of the full nutrient series, as these plants were used 
for a study of some of the physiological conditions of the plants at 
wilting time. One point, of vital interest here, is the amount of 
adjustment to concentrated solutions which the plants may have 
made. 
The cell sap of the roots of normal wheat plants is isotonic with 
solutions which contain a concentration of sodium chloride lying 
between 3 per cent. and 6 per cent. A plant was removed from 
the tumbler of the 0.8 per cent. set, after all the plants in the 
tumbler, save this one, had wilted. The plant was removed by 
sluicing with a small stream of water, a number of uninjured root 
tips thus being obtained. The root tips were placed on a slide, 
under the microscope, and the concentration of the cell sap in 
cells of the tip was determined by the plasmolytic method. There 
was no plasmolysis with a 3 per cent. sodium chloride solution. 
A 6 per cent. plasmolyzed. Turgor was restored by tap water, 
the cells appearing normal in every way. The plants, therefore, 
did not adjust themselves to the various soil solutions by materially 
increasing the concentration of their cell sap. 
There were, however, visible modifications in the plants due 
to the influence of the salts added. Increase in the amount of 
bloom, as mentioned by Harter,’ was not observed, but there was 
a uniform decrease in the rate of transpiration. The leaves of 
the plants grown in the higher concentrations felt harsh to the 
fingers. A microscopical study of the leaves was not made, but 
possibly this harshness was due to some modification in the struc- 
ture of the cell walls, as found by Harter. As mentioned above, 
there was a correlation between the size of the plants and the 
amount of salts added, the plants in the higher concentrations 
being much smaller. This is of special interest, for not only was 
the area of leaf surface reduced, in plants grown in the higher 
concentrations, but their root systems were proportionately re- 
duced. In the 0.8 per cent. set the roots developed only in the 
upper one third of the tumblers. It follows, therefore, that the 
