326 BOTANICAL GAZETTE [OCTOBER 
in fully turgid cells is equal to that of pure water, and of plasmolyzed cells to 
that of their cell sap. The vapor pressure of plasmolyzed cells with 100 atmos- 
pheres osmotic pressure is 7 per cent less than that of pure water. (2) Water 
movement in parenchyma is dependent upon difference in degree of turgescence 
and independent of difference in osmotic pressure. (3) If in a wilted leaf the 
osmotic pressure of the parenchyma is P atmospheres, there exists in the 
adjacent vessels a tension of P-1 atmospheres, and the vapor pressure of 
the water in the vessels is correspondingly reduced. (4) The energy potentials 
for moving water in the plant are the potential differences in imbibitional 
energy, osmotic energy, and hydrostatic pressure. These potentials originate 
from the transformation of a part of the energy potential which exists between 
the surface cells and the atmosphere in the way of vapor pressure differences. 
The rest of the primary potential is usable by Te alone. 
In the experimental part RENNER makes use the annulus of fern 
sporangia (Polystichum Filix-mas) for measuring the slain strength of water 
under the conditions in which it. exists in plant cells. The walls of these cells 
are impermeable to cane sugar in aqueous solution, and to certain substances 
in very low concentration within the cells, but they are more or less permeable 
to salts. In a solution of cane sugar with an osmotic pressure of 200 atmos- 
pheres the annulus cells are deformed and the sporangia opened, but no gas 
BeiEAee are formed within the cells (there is not a throwing movement of the 
angia), although the water within is stretched equivalent to about 200 
Haken eres. Since the osmotic pressure of sugar solutions was not sufficient, 
and the walls were permeable to salts, RENNER turned to the vapor pressure 
method of determining the tensile strength of the water within these cells. 
Over a saturated solution of sodium chloride almost all of the sporangia 
spring with the formation of gas bubbles in the annulus cells. In the few 
not springing, the water in the annulus cells must be stretched approximately 
equivalent to the osmotic pressure of the solution, 368 atmospheres. There 
was little springing of the sporangia until the solutions used exceeded 300 
atmospheres osmotic pressure. 
Working independently, but with similar methods, UrspruNnc‘ concludes 
that the water in annulus cells of fern (Pteris, Scolopendrium) sporangia are 
under a tension (a stretch) of somewhat more than 300. atmospheres at the 
time most of the sporangia spring. These determinations of cohesion exceed 
the values obtained by Drxons in his measurements in glass tubes. 
HAtte,’ a student of RENNER, finds that generally when plant cells lose 
water by evaporation the protoplasm is not immediately withdrawn from the 
4 Ursprune, A., Uber die Kohision des Wassers im Farnannulus. Ber. Deutsch. 
Bot. Gesells. 33:153-162. 1915. 
5 Bor. GAZ. 60:74, 75. 1915. 
6 HaLLe, Hans, Untersuchungen iiber Welken, Vertrocken, und Wiederstrafi- 
werden, Flora 108:73-126. 1915. Written by RENNER after the death of HALLE at 
the front. 
