59 2 
Notes. 
Since allowance had to be made for the respiration, this was taken 
for each temperature under exactly similar conditions to those existing 
in the corresponding assimilation experiments. A good curve showing 
the gradual increase of the respiration with the temperature was obtained. 
The lowest temperature at which assimilation could be detected 
was — 6° C. This is the first well-established case of assimilation 
below o° C. 
For temperatures between — 6° C. and 33°C. it was found that 
assimilation is affected in exactly the same way as is respiration. 
Provided the illumination is sufficient, the assimilation increases with 
the temperature. At any given temperature the leaf is only capable 
of a limited absolute amount of assimilation, and increase of illumina- 
tion beyond the amount requisite for this maximal amount produces 
no further effect at all. A greater assimilation can only be obtained 
by increasing the temperature. Thus the fundamental condition 
regulating the assimilation is the temperature, the intensity of the 
light occupying a secondary position similar to that of the percentage 
of carbon dioxide. This simple conception of the relation between 
temperatures and assimilation stands quite apart from all previous views. 
For temperatures above 33 0 C. the result is complicated by the 
injurious effects of the temperature. The fatal temperature for Cherry 
Laurel leaves is in the region of 41-45° C., but the specific resistance 
of the individual leaves is very variable. Death is shown by a rapid 
decrease in the respiration, but it may be several hours before this 
ceases entirely. Exposure to light has a most marked effect in in- 
creasing the resistance of leaves to the effect of high temperatures. 
Most interesting results were obtained from the prolonged exposure 
of leaves to high temperatures. It was found that the respiration of 
a leaf in the dark falls off much more rapidly than that of a leaf in the 
light, and the former can in no case be taken as a measure of the 
latter. At first assimilation and respiration are equally and similarly 
affected by the temperature, but later the assimilation ceases, while 
respiration is still active. 
GABRIELLE L. C. MATTHAEI. 
Cambridge. 
