Wounded Plants. 
54i 
injured conditions there is an appreciable rise in the fraction, 
there is no other marked change in the relations except 
during the first few hours after injury. The absorption of 0 2 
is always greater than the production of C0 2 , except at the 
time already referred to, when the latter gas almost equals 
or slightly exceeds the former in quantity (Expts. 37 , 41 ). 
There is a slight tendency to an increase of the C0 2 in 
relation to the 0 2 at the time of the maximum respiration, 
which, however, falls off again somewhat as the respiration 
decreases. 
In the experiments with more active tissues, for which 
seedlings of Vicia Faba were taken, results of a less constant 
nature were obtained. But in most cases a distinct increase 
in the respiration was found, rising to a maximum at a some- 
what variable time after injury, and falling again to approxi- 
mately the original amount as before injury. Necessarily, 
owing to the changes taking place in the seedlings during the 
course of the experiment, the reaction to injury was at times 
dwarfed by other causes. Stich, who experimented with 
a considerable range of seedlings, found a great diversity in 
the amount of respiration, but usually he records a distinct 
increase after wounding. One fact to be noted in the experi- 
ments with seedlings is that no sudden evolution of C0 2 is to 
be found directly after injury. This is also true of leaves, 
which show, however, a rise and fall in the respiration, as 
do other injured plants, although, necessarily from their short 
life after separation from the plants on which they grow, it is 
not for long. 
Such, then, are the general facts connected with the pheno- 
mena of the respiration, which raise a number of questions 
that require a more detailed discussion of some of the experi- 
ments to answer. The first question is of course what, on 
the whole, is the cause of the increased respiration. As has 
already been said, Bohm 1 concludes there is no doubt that 
the cause of it is alone the irritation of the wound itself, and 
not the increased opportunity for the action of the oxygen of 
1 Bot. Centralblatt, Bd. 1 , p. 200. 
