30 Richards . — The Evolution of 
Vallisneria ), a marked streaming is seen after injury to 
neighbouring parts. But in relation to the subject of this 
paper, the effect of injury or other abnormal conditions on 
the functions of the plant as a whole is of particular interest. 
One of the best measures of increased activity of a plant is 
found in the intensity of the respiration ; and this last has 
been determined, under a variety of irritating influences, to be 
temporarily considerably above the normal. For instance, 
under exposure to the vapour of chloroform or ether 1 , or to 
various gases in increased or diminished pressure 2 , and also 
after wounding 3 , the C0 2 -production rises markedly, and in 
the last-mentioned case at least subsequently falls to the 
normal. 
It would seem then possible that all this extra work which 
is done under the stimulus of irritation, would necessitate a rise 
in the temperature of the affected parts. So it was suggested 
to the writer during his work on the respiration of injured 
plants, and so also had Pfeffer forecast the possibility of an 
increase in the temperature of plants through wounding 4 . 
To measure any rise of temperature on the wound-surface 
itself, it is of course quite impossible to employ a ther- 
mometer ; instead of which a thermo-element, of which a 
description will be given later, was used. The results of 
the experiments attained by this method, and also on a large 
scale with a rough calorimeter, were sufficiently successful to 
warrant an account of them. The writer has again to thank 
Professor Pfeffer very much for his advice and criticism, and 
for the facilities afforded in the laboratory. In this place also 
the writer would express his obligation to Dr. Giessler, one 
of the assistants in the Botanical Institute at Leipzig, wdiose 
invaluable assistance, in the many operations which required 
two persons to carry out, contributed greatly to the success 
of the work. 
1 Elfving, Ofversigt af Finska Vetensk-Soc. Forhandlingar, Vol. xxviii, 1886. 
2 Johannsen, Untersuch. Tiibingen, I. 686. — Stich. Flora, 1891, p. 1. 
8 Richards, Respiration of Wounded Plants, Ann. of Bot., Vol. x, p. 532, 1896. 
4 Studien zur Energetik der Pflanze, 1892, footnote 2, p. 201. 
