705 
the Respiratory Exchanges of Leaves. 
a greatly diminished production of C 0 2 . Miss Irvings experiments, in 
which the C 0 2 production was determined from the first moment of the 
introduction of chloroform, show that the first effect here also is to increase 
the production of carbon dioxide ; but the stimulation is of short duration. 
How the rate of absorption of oxygen is affected in this very transient 
initial phase has as yet not been determined, nor the course of the change 
from stimulation to the onset of irreversible changes : in my experiments 
these stages were passed through in the chloroforming vessel. 
In order to determine whether the marked absorption of oxygen which 
accompanies disorganization in leaves of Cherry Laurel be a general pheno- 
menon, similar experiments were made with other leaves. Some experi- 
ments with leaves of Portugal Laurel showing a similar inrush of oxygen 
have already been referred to. These leaves change at the same time to a 
very dark chocolate colour. Experiments were also made with leaves of 
Helianthus tuber osus and Tropaeohim majus. 
Experiments with Helianthus tuberosus. 
In the leaves of Helianthus tuberosus disorganization is accompanied 
by a blackening of the leaf, and if the dose of chloroform is sufficiently large, 
by the exudation of water and marked flaccidity. 
In the first two of the following experiments the dose was small and 
the leaves showed none of these signs of disorganization. 
Experiment VI. August 24, 1910. Dose, 0*05 c.c. for ten minutes. 
Temperature, 17*6-19° C. Eight starved leaves weighing 1 2-6 grammes. 
The leaves were respiring at a low rate, having been in the dark for 
Fig. 7. 
seven days. Here, as in the case of Cherry Laurel, a small dose of chloro- 
form augmented the respiration, affecting both the production of C 0 2 and 
the absorption of oxygen. The respiratory quotient, however, appeared to be 
distinctly lower, the absorption of oxygen having been the more affected. 
Here, too, the maximum rates were attained at once, and the curves fell 
from the beginning, instead of rising to a later maximum as in Experiments 
