1085 
tipon Respiration and Assimilation. 
was employed to hasten the filtration. For this purpose the top of the 
pipette was connected by stout tubing to a bulb of air, the pressure on 
which was adjusted by a head of mercury. 
The air-current through the apparatus travelled at the rate of a litre 
per hour, and the amount of liquid chloroform percolating per hour is there¬ 
fore a measure of the concentration per litre of air in contact with the leaf. 
This apparatus was not satisfactory for giving very strong con¬ 
centrations, because when more than 1 c.c. of chloroform filtered through 
in an hour, it did not all vaporize at the ordinary temperatures, but collected 
in the anchor tube in the liquid form. To give stronger concentrations the 
‘anchor tube’ was abandoned and the air-current led through a bulb 
half full of chloroform and sunk in the water-bath so as to be at a 
temperature of 25 0 C. The rate of vaporization in this case was determined 
by control experiments. 
The experiments in this section are carried out partly with Barley 
shoots, in fifteen-gramme lots, as before; and partly on Cherry Laurel. 
In this latter case a single leaf was used for each experiment, and as the 
weights of these vary, the C 0 2 -numbers are not directly comparable either 
with other Cherry Laurels or with the Barley shoots. The single leaves 
were not enclosed in a glass jar, but were set up in the oval leaf-chamber 
figured in ‘ Assimilation and Respiration, VII * (op. cit.). 
The series of C 0 2 -estimations fluctuates much more with single leaves 
(Cherry Laurel) than with groups of leaves (Barley) in which the individual 
fluctuations partly equalize one another. 
Experiment VII. Concentration of Chloroform =0*046 c.c. per litre of 
air-current. A single leaf of Cherry Laurel weighing 1*55 grms. was 
Fig. 9. 
set up in the flat leaf-chamber and two normal respiration readings taken 
before chloroform was given. These gave values of 0*0009 and 0*0007 g rm * 
respectively (Fig. 9). The chloroform was then administered, and in 
4 B 
