Note * — Chapter IV · THE EFFECTS OF HEAT ON THE LEAVES.

When my experiments on the effects of heat were made, I was not aware that the subject had been carefully investigated by several observers. For instance, Sachs is convinced (‘Traité de Botanique,’ 1874, pp. 772, 854) that the most different kinds of plants all perish if kept for 10 m. in water at 45° to 46° Cent., or 113° to 115° Fahr.; and he concludes that the protoplasm within their cells always coagulates, if in a damp condition, at a temperature of between 50° and 60° Cent., or 122° to 140° Fahr. Max Schultze and Kühne (as quoted by Dr. Bastian in ‘Contemp. Review,’ 1874, p. 528) “found that the protoplasm of plant-cells, with which they experimented, was always killed and [[page 67]] altered by a very brief exposure to a temperature of 118 1/2° Fahr. as a maximum.” As my results are deduced from special phenomena, namely, the subsequent aggregation of the protoplasm and the re-expansion of the tentacles, they seem to me worth giving. We shall find that Drosera resists heat somewhat better than most other plants. That there should be considerable differences in this respect is not surprising, considering that some low vegetable organisms grow in hot springs—cases of which have been collected by Prof. Wyman (‘American Journal of Science,’ vol. xliv. 1867). Thus, Dr. Hooker found Confervae in water at 168° Fahr.; Humboldt, at 185° Fahr.; and Descloizeaux, at 208° Fahr.) [page 67]