xu, c,1 Brown and Heise: Carbon Dioxide Assimilation 5 
From these figures the authors calculated that the coefficient 
of increase for 10° was 2.05. This coefficient, those calculated 
from van Amstel’s data, and the coefficients from the experi- 
ments of Blackman and Smith are brought together in Table 3. 
The steady fall in the coefficients as higher temperatures are 
reached is similar to that usually shown by vital phenomena. 
However, the coefficients are much smaller than those generally 
shown by physiological processes. The coefficients between tem- 
peratures of 13° and 40° are within the range of those for photo- 
chemical reactions. Table 3 shows that if the results were in 
the form of a curve the limits within which photochemical 
coefficients would hold could be extended, somewhat, in both 
directions. 
TABLE 3.—Coefficients of increase in the rate of carbon dioxide assimila- 
tion in Elodea with rises in temperature. 
[All coefficients are calculated on the basis of a rise of 10° C.J 
Range of 
——_ roan Calculated from data of— 
ature. ? 
°C. 
7-13 2.05 | Blackman and Smith, p. 402. 
7-21 1.75 | Blackman and Smith, pp. 400, 401. 
18-21 1.35 Do. 
24-36. 5 1.28 | Van Amstel. 
36. 5-40 1.25 Do. 
a 
These experiments suggest that the temperature coefficients 
for photosynthesis in Elodea bear about the same relation to 
photochemical ratios that those of most vital phenomena do to 
the van’t Hoff principle. 
THE WORK OF KREUSLER ON RUBUS FRUTICOSUS 
The work of Kreusler has been much quoted as showing the 
relation between temperature and assimilation. These papers 
are not available. Pfeffer ** gives a curve showing the results. 
From this curve the coefficients for the rate of increase in assimi- 
lation have been calculated on the basis of a rise in temperature 
of 10°. The numbers may be slightly different from what they 
would have been if based on the actual figures, but they are 
certainly accurate enough for our purposes. The results are 
* Pfeffer, W., Physiology of plants, 2d ed., translated by A. J. Ewart 
(1900) 337. 
