xu, c,1 Brown and Heise: Carbon Dioxide Assimilation 19 
from 3.6° to 33.1° had no appreciable effect on assimilation. 
Therefore, we may assume that the value of unit intensity of 
light at 30.5° would be the same as in fig. 3. An examination 
of Table 6 indicates that this would also hold for light intensity 
of two units. It is probable that the intermediate points would 
also be the same. 
Since the curve for the different light intensities at the highest 
temperature would, apparently, be the same as that in fig. 3, we 
would seem to be justified in assuming that the different rates 
of assimilation, shown in fig. 3, are due to changes in the inten- 
sity of the light; and that temperature was nowhere a limiting 
factor. 
An examination of Tables 5 to 7 will show that with a constant 
intensity of light and temperatures above 3° the coefficient of 
increase in assimilation with a rise of temperature of 10° is 
1.00 or slightly more than this for the three series with unit 
intensity of light (fourteen experiments) in Table 5, for light 
intensitiy of eight units (six experiments between 25.3° and 
38.30°) in Table 7, and for one (six experiments) and two 
(three experiments) units in Table 6. The two figures in Table 
6 for six units give a coefficient of 1.17. The highest and lowest 
values for assimilation with four units in Table 6 show a coef- 
ficient of 1.38; although, as we have seen, the figures on which 
this is based cannot be regarded as reliable, and the coefficient 
probably should be lower. The above coefficients are within 
the range that would be expected for a photochemical reaction. 
With increasing light intensities the rise in assimilation per 
unit of light was less and less, indicating that the reaction veloc- 
ity is not directly proportional to the light intensity. That this 
is in agreement with the results of Pantanelli** on Elodea is 
very apparent, if the values are taken from his curve in 
Table IV. 
These results are quite in keeping with those of nonvital 
photochemical reactions, many of which show great deviations * 
from a direct proportionality between light intensity and reac- 
tion velocity. Increasing the light increased the assimilation 
but apparently had little or no effect on the temperature coef- 
ficients. With continued increases in light intensity we ap- 
parently must reach a point where rises in the rate of assimi- 
* Pantanelli, E., Abhangigkeit der Sauerstoffausscheidung belichteter 
Pflanzen von Ausseren Bedingungen, Jahrb. Wiss. Botanik 39 (1904), 
167—228. . 
* Weigert, F., Die chemischen Wirkungen des Lichts, Sammlung Chem.- 
Techn. Vortriige 17 (1912) 264. 
