Osmotic Properties of some Plant Cells at Low 
Temperatures. 
BY 
FRANCIS J. LEWIS, D.Sc., F.R.S.E. & C , F.L.S., 
AND 
GWYNETHE M. TUTTLE, M.Sc., 
Botanical Department , University of Alberta, Edmonton , Canada. 
With five Figures in the Text. 
Contents. 
PAGE 
VI. Amount of Under-cooling and 
a of Leaves . . . .411 
VII. Condition of Cell Contents 
at Low Temperatures . . 413 
VIII. Discussion 415 
IX. Summary 415 
Introduction. 
D URING the last few years the cryoscopic method of determining the 
osmotic pressure of plant saps has largely replaced the older plasmo- 
lytic methods. Investigations have been directed to seasonal changes in the 
constitution of the sap, as well as to changes due to differences in habitat, 
both in the same species and in different species characteristic of various 
plant formations. 
The most recent work dealing with the first aspect of the subject is the 
work published by Dixon and Atkins in the Proc. Royal Dublin Society (5). 
These authors have carried out a fine series of researches on the seasonal 
changes in osmotic pressure and the relative proportion of electrolytes and 
non-electrolytes in the cell sap/ both in leaves and in the conducting tissues 
of stems and roots of various plants. This work was directed particularly 
to the elucidation of the part played by osmotic pressure in the ascent of 
sap. Attention was paid to methods of extracting the plant sap to ensure 
that the extract was a fair sample of the sap within the living cell— a matter 
to which but little attention had been paid by previous workers. 
[Annals of Botany, Vol. XXXIV. No. CXXXV. July, 1920.] 
PAGE 
I. Introduction .... 405 
II. Scope of Work .... 406 
III. Methods 407 
IV. Meteorological Conditions . 408 
V. Records of Osmotic Pressures, 
Electrolytes, Non-Electro- 
lytes, and Sugars . . . 408 
