THE 
NEW PHYTOLOGIST 
Vol. XXII. No. 5 December i, 1923 
ON THE PHENOMENA ATTENDING SEASONAL 
CHANGES IN THE ORGANISATION IN LEAF 
CELLS OF PIGEA CANADENSIS (Mill.) B.S.P. 
By FRANCIS J. LEWIS, D.Sc. 
AND 
GWYNETHE M. TUTTLE, M.Sc. 
Botanical Laboratories, University of Alberta, Edmonton, Canada 
CONTENTS 
PAGE 
1. Introduction. ...... 225 
2. Meteorology ....... 226 
3. Physical conditions of sap during conversion 226 
4. Conditions affecting conversion . . . 229 
5. Summary ....... 232 
Introduction 
O bservations have been carried out by us for several seasons 
on the periodic changes which occur in the organisation of the 
cells and the physical conditions of the saps of winter evergreens in 
Northern Alberta. On account of the long winters and the extremely 
low temperatures to which the leaves are resistant, observations in 
N.W. Canada are of interest; for as far as we are aware no observa¬ 
tions have been carried out on evergreen leaves under these conditions. 
The work of Lidforss(i) on the winter evergreens of Sweden 
although containing much information as to the changes in the 
reserve materials and the causes of immunity to cold, does not deal 
with the physical conditions of the sap; in addition the length 
and severity of the Swedish winter does not compare with the 
winters of Northern Alberta. 
In a previous paper (2) four native plants were examined through¬ 
out the winter, attention being directed to the osmotic pressures, 
Phyt. XXII. 5. 
15 
