43 
Heat by Wounded Plants. 
onion is more or less, though somewhat irregularly, affected, 
and that at so great a distance as 45 mm. from the wound 
a temperature of 0-17° C. over that of the uninjured bulb was 
found, when it was only 0-28° C. in the wound itself. It is, 
then, easy to believe that the small onions used in the bell- 
glass experiments, and injured so severely as by quartering, 
should give a comparatively violent reaction. 
From the above discussion of the results of the experiments 
it is evident that there is a distinct temperature-reaction, more 
or less variable, which manifests itself in plants after injury. 
This reaction is in fact a fever , if one may use the term, 
brought about by the increased vital activities of the wounded 
plants. In considering the significance of this ‘ wound-fever * 
one should also bear in mind the other phenomena which 
attend injury. Attention has already been called to these in 
the introduction to this paper. Of the greatest interest is the 
consideration of the relation which the increase in respiration 
bears to the rise in temperature. The respiration-curve was 
found to be at its highest, in potatoes for instance, about twenty- 
four hours after wounding ; and it is at the same time that the 
maximum of the temperature-curve is indicated (Woodcut 2). 
In the same way, as has already been said, the phenomena go 
hand-in-hand in the case of leaves. The return of the tem- 
perature to the normal is, it is true, somewhat more rapid 
than that of the respiration, at least as far as was indicated 
by the method used ; but after the fourth or fifth day it will 
be remembered that even the respiration is only very slightly 
above the normal 1 . Theoretically speaking, the rise in respira- 
tion, representing as it does an increase of chemical work 
in the tissues of the plant, demands a rise also of temperature, 
and it is interesting to find that, as a matter of fact, such 
is the case. Even granting that the respiratory processes 
are alone responsible for all the heat normally produced in 
a plant, the temperature could hardly be expected to increase 
correspondingly with the respiration. The writer would 
again call attention to the fact that by radiation and so 
1 See Richards, Respiration of Wounded Plants, 1. c. 
