1910.] On Vegetable Assimilation and Respiration. 4.03 
assimilation and each of the three factors, CO2-supply, temperature, and 
illumination separately. 
The two latter curves are based on the data set out in this section, the 
particular points established being marked with circles; the curve for CO: 
supply is taken from fig. 1. We can by inspection tell exactly what 
minimum of COs, temperature, and light will be required for any one of the 
values of assimilation on the ordinates by following the horizontal line 
right across the diagram and noting where it intersects the three curves 
respectively. 
-Reciprocally, given any hypothetical combination of different magnitudes 
of the three factors, we have only to note in the diagram the values of 
assimilation corresponding to each of them, and we can foretell that the 
value of assimilation actually attained in that combination will be the lowest 
of the three values. 
Section 1V.—CRITICAL ANALYSIS OF THE RESULTS OF PREVIOUS WORKERS. 
Instead of prefacing the present paper by the usual summary of previous 
work, we have thought fit to expound our own point of view first, and we 
now proceed to some critical account of the work of other investigators. This 
order is adopted because we differ from them in the interpretation to be put 
upon the facts of assimilation rather than in the nature of the facts them- 
selves. We may confine ourselves to the works of Reinke,* 1883; 
Treboux,t 1903; and Pantanelli,t 1903. 
Reinke counted the bubbles given off by Elodea in spring water with a 
little added COs, when it was exposed to a series of lights of different 
intensity§ in rapid succession, After the plant had been about one minute 
in.a given illumination the number of bubbles liberated in two successive 
quarter minutes was counted, and then the intensity of the light was altered 
and a new reading started. Increasing the light from 1/24 to 1/2 sunlight 
* J. Reinke, “ Untersuchungen ii, d. Einwirkung des Lichtes auf die Sauerstoff- 
ausscheidung der Pflanzen,” * Bot. Zeit.,’ 1883, p. 697. 
+ O. Treboux, “Hinige stofiliche Einfliisse auf die Kohlensiure-Assimilation bei 
submersen Pflanzen,” ‘ Flora,’ 1903, p. 53. 
{ E, Pantanelli, ‘‘Abhangigkeit der Sauerstoffausscheidung belichteter Pflanzen von 
dusseren Bedingungen,” ‘ Jahrb. f. wiss. Bot.,’ 1903, vol. 39. 
§ Reinke placed his plant, within a dark room, in the path of a beam of sunlight 
concentrated by a large lens of long focus. By adjusting the distance of the plant 
beyond the focus of the lens he obtained positions corresponding to a series of definite 
illuminations, ¢.¢., 1/36, 1/25, 1/16, 1/9, 1/4, 1/1, 4/1, 9/1, 16/1, 25/1, 36/1, 49/1, and 64/1, 
these being fractions of the direct sunlight falling at the moment on the lens from a 
heliostat. Pantanelli used also the same method of obtaining definite intensities of 
light. 
