38 
JOHN H. EHLERS 
these plants, when exposed to sunUght at temperatures as low as 
— 30° to — 40° C, absorb CO2 and evolve oxygen, while respiration 
ceases at — 10° C. He suggests that the absorption of heat along 
with the light rays by the exposed leaves may prevent the cell sap 
from being entirely frozen at even these low temperatures and that, 
in consequence, assimilation may proceed. 
Pfeffer (20) offers in criticism of Jumelle's results the following: 
"Since, however, all respiration ceases at — 10° C. to — 12° C, it is 
manifestly impossible that any assimilation of carbon dioxide can 
take place at — 40° C, for CO2 assimilation is a vital process involving 
protoplasmic activity." Jumelle's methods are generally considered 
faulty by later investigators, and not much credence is placed in his 
results. For criticism of his methods the reader is referred to Matthaei 
(15) and to Ewart (7). 
Miyake (18) has found that the leaves of a large number of ever- 
green plants, including trees, shrubs, and herbacous plants growing 
in the vicinity of Tokyo, contain more or less starch during the winter. 
To determine whether this starch was the product of photosynthesis 
in winter, or whether it was stored there as suggested by Sachs (25), 
he excluded light from several plants {Thea japonica, Fetsia japonica, 
Cinnamomum Camphora, Pinus Thunhergii, and Abies firma), some 
in the open, others in a dark chamber the temperature of which 
varied between 1° and 7° C, until the starch had disappeared, and 
then exposed them to sunlight. Microscopical tests showed the 
reappearance of starch within five hours after exposure. The tem- 
peratures were: for Thea, minimum 2.6° C, maximum 8.6° C, mean 
3.1° C; for Fetsia, minimum 0.8° C, maximum 9.7° C, mean 3.4° C. 
He concludes that starch is formed by photosynthesis in winter and 
that its translocation occurs in the same season. This is further 
evidence, not only of photosynthesis in winter, but also of the accumu- 
lation of reserve material. The temperatures given were taken from 
the records of the Meteorological Observatory of Tokyo, and, pre- 
sumably, are shade temperatures and, therefore, do not represent the 
true temperature of the leaf. As will be shown later, the absorption 
of the sun's radiations by the leaf will increase the internal temperature 
of the leaf from 3 to 10 degrees Centigrade on bright winter days. 
The next contribution of importance was by Ewart (6). In a 
paper on assimilatory inhibition he devotes a part to experiments 
on assimilation at low temperatures. He used the bacterium method. 
