709 
the Respiratory Exchanges of Leaves. 
intervals of an hour each. Here the result corresponded with that in 
Experiment VIII, since the very high rate of absorption of oxygen, the 
highest obtained, was confined to the first short interval. The results were 
as follows : 
c.c. per hour per leaf. 
co 2 
After chloroform, 17 minutes 
O’ 20 
i-8o 
next 63 „ 
O’ 2 1 
o*45 
60 „ 
0*14 
0-31 
Doubtless the brevity and rapidity of the inrush of oxygen revealed in 
this experiment and in Experiment VIII always characterizes the absorp- 
tion of oxygen which accompanies the beginning of disorganization in 
leaves of Helianthns : in the other experiments the first sample of air was 
not taken soon enough to show this feature so clearly. 
Treatment of leaves of Helianthus tuberosus with chloroform to the 
point of disorganization resulted, therefore, in a marked absorption of 
oxygen very similar to that observed in the case of Cherry Laurel. Here, 
again, it was correlated with the change of colour due to oxidation of 
tannin. Small doses, too, evoked a temporary augmentation of both pro- 
duction of C0 2 and absorption of oxygen. 
It is clear, however, that chloroform penetrates the more delicate leaves 
of Helianthus much more readily than the better protected leathery leaves 
of Cherry Laurel. Whereas in the case of the latter a dose of o*2 c.c. in the 
litre vessel usually left the leaves green for at any rate a long time, this was 
not always so in the case of Helianthus , even after a dose a quarter as big 
(0-05 c.c. per litre). 1 It is not unlikely, as a further consequence of this 
difference, that in some of the experiments with doses a little larger, 
especially where the leaves were exposed but for a short time to the chloro- 
form vapour, most of it was absorbed by the outer layers of cells. 2 The 
results, some of which show stimulation of the C 0 2 output as well as the 
much accelerated C 2 intake associated with disorganization, may therefore 
be complex, like those with Cherry Laurel, in which different parts of the 
leaves were differently affected. 
The most striking feature of the results is the sharpness and relative 
brevity of the acceleration in the absorption of oxygen. It has already 
been remarked that the curve of 0 2 absorption in the case of leaves of 
Cherry Laurel exposed to a fatal dose falls very rapidly at first and slowly 
later. The same is more distinctly shown by the experiments with Heli- 
anthus, where a first short period of enhanced 0 2 absorption appears to be 
quite sharply distinguishable. This is illustrated in Fig. 13, in which the 
1 Cf. Weevers: Betrachtungen und Untersuchungen iiber die Nekrobiose und die letale Chloro- 
ormeinwirkung. Recueil des travaux bot. neerland., ix, 1912, p. 255, &c. 
2 Weevers records the coloration of the epidermis alone in petals of Magnolia. Loc. cit.,p. 252. 
3 c 
