The Evolution of Heat by Wounded Plants* 
BY 
HERBERT MAULE RICHARDS. 
With Woodcuts i and 2. 
T HE capability of plants to respond by increased vital 
activities to different forms of injury is a fact which 
is well recognized, although the attending phenomena have 
not in all cases been thoroughly investigated. It is not 
difficult to enumerate a number of instances where, in quite 
dissimilar ways, a definite reaction towards abnormal condi- 
tions has been observed. There may be mentioned, for 
instance, the formation of callus and of corky tissue, which 
follows injury; or the abnormal growths of tissue attending 
the irritation caused by animal parasites (galls) or by parasitic 
Fungi. In such cases the evidences of unusual activity on the 
part of the plant is shown in the morphological differences of 
the affected tissue. From an entirely different standpoint, 
that of the stimulus of the ordinary functions of the cells 
themselves, the work of Hauptfleisch 1 affords interesting 
evidence. It appears from his observations that the move- 
ment of protoplasm is accelerated to an unwonted degree 
by injury to adjoining cells. In some plants, where under 
ordinary conditions no motion is observable (e.g. Elodea , 
1 Prings. Jahrb., Vol. xxiv, p. 190, 1892. 
[Annals of Botany, Vol. XI. No. XLI. March, 1897.] 
