1910. | On Vegetable Assimilation and Respiration. 385 
(3) The temperatures of the bath and of the inside of the chamber were 
noted at intervals, as the entries in Table I show. The latter is always a 
little higher than the bath, due to the non-assimilatory radiation absorbed by 
the green leaf. The average temperature of the chamber, throughout the 
experiment, was 20°3 C. 
(4) The richness in CO: of the medium which bathes the leaves is of great 
importance. The uumber adopted must be the mean between the CO»- 
content of the liquid entering the chamber and of that leaving it. The 
average of the last seven readings for the affluent gives 25°79 ec. N/10 HCl 
as the content of 200 e.c. of the liquid entering the chamber. The corre- 
sponding number for the effluent is 19 cc. So the mean content of the 
chamber equals 11:20 c.c. N/10 HCl per 100 cc. of liquid = 0:0279 grm. COz 
per cent. (1 c.c. standard acid being equivalent to 0°00249 erm. CQs). 
(5) The difference between the COs-content of the affluent and effluent 
gives in its uncorrected form the measure of the CO2 which has disappeared 
from the chamber, chiefly, of course, by photo synthesis in the green tissues. 
Here it is 6°79 N/10 HCl = 001693 erm. COs per 200 c.c. of solution, and 
this figure has to be calculated per hour (6), and corrected for bubbles (7) 
and respiration (8). 
(6) The current rate is measured throughout the experiment by collecting 
all the effluent liquid in the measuring cylinders, F and G. 
The outflowing liquid shifts from cylinder F to G every time the current 
is diverted from pipette D to E, and wice versd, so that the volumes of 
effluent recorded in the table come alternately in F and G at rather 
irregular intervals of time. The actual volumes in the cylinders* are 
given in Table I and in brackets beneath each the rate per hour calculated 
from it. The average rate between 12.45 and 7 P.M. works out at 316°5 c.c. 
per hour. Therefore the weight of CO, lost per hour in the chamber is :— 
316°5 
001693 x Te 002679 grm. 
(7) The amount of CO. escaping into the gas-bubbles formed must be 
ascertained and subtracted from the value in (6). 
The gas evolved as bubbles was automatically collected over mercury in 
the receiver Z from 11.25 a.m. throughout the experiment as shown in the 
last column of the table. At 3.36 the amount collected was passed into the 
eudiometer for analysis. At laboratory temperature and pressure its total 
volume was 37°3 «.c., of which 4°8 cc. proved to be CO2; = 1:2 cc. CO2 
per hour. At 6 P.M. the gas collected since 3.36 was again withdrawn and 
* The contents of the cylinders are read off at frequent intervals to see if sufficient 
constancy is being maintained ; if not, readjustment is made. 
NiO. laxXX Xi b.—-B, Dae 
