546 Richards. — The Respiration of 
in the tissues, as is indicated by the fact that practically all 
of it came off at once on warming. It was only desired to 
determine in a general way if there was much or little C 0 2 , as 
such, in the tissues, and not to arrive at a definite quantitative 
result. That there appears to be a considerable amount agrees 
with the other experiments discussed, and supports the view, 
already expressed, of the source of the first rush of C 0 2 
immediately after injury. 
It was also desired to find if an increase of injury brought 
about a corresponding increase of respiration. As is shown 
in Experiments 6 and 1 8 , there is a certain increase when 
the plant is further wounded, both in the case of potatoes 
and carrots, but one that does not bear any distinct relation 
to the amount of injury done. As before, leaves give an 
opportunity of more or less eliminating the question of 
aeration, and allowing a better means of observing the effect 
of the irritation alone. The leaves of Veronica and Acacia 
(Expt. 32) were experimented with from this standpoint. 
The latter was the better, although the former also served 
to show the reaction to some extent. With the Acacia the 
large compound leaves were taken from the plant, and 
determinations were made until it was found that the injury 
caused by the cutting of the petioles had passed its maximum. 
The pinnae were then cut off, and the main stalks once or 
twice cut across ; as a result, the respiration rose a second 
time to a slightly higher point. When the evolution of C 0 2 
was once more on the wane, the leaves were injured for a 
third time, and more severely than before, by stripping off 
the pinnules and longitudinally slitting all the stalks. On 
this occasion the increase was much more strongly marked, 
and finally stopped on the gradual death of the leaves. This 
experiment shows then quite plainly that a certain effect 
is produced by increase of injury, although it must be 
remembered that in this case it was not possible to wash 
away the injured cells as was always done with longer tissues. 
An examination of the results obtained with the apparatus 
already described for the comparison of the amount of C 0 2 
