M. Dutrochet on the Temperature of Vegetables. 107 



the same hour. On the third day of obscurity, the paroxysm 

 did not return. Exposure to simple diifuse hght, is all that is 

 necessary quickly to restore to the plant the proper heat it 

 has lost. 



I wish to compare the proper heat of vegetables with that 

 of some animals of lom temperature. I make use of this ex- 

 jiression because I do not think that there are any cold ani- 

 mals, that is, absolutely deprived of a proper heat. I have 

 found that the heat of vegetables is generally little inferior to 

 that of insects, and is often superior to it. The proper heat of the 

 frog (Eana esculenta) is much inferior to that of most plants. 

 I have found no appreciable heat in the crawfish ( Astacus 

 fluviatilis), nor in the slug (Limax rufus). Thus vegetables 

 are placed higher in the scale than certain animals with re- 

 lation to the degree of their proper heat. 



M. Becquerel having stated that he found the temperature 

 of the living branch of a tree several degrees higher than in a 

 dead one, M. Dutrochet, in a subsequent note (July 1st) re- 

 marks : When I formed the plan of making investigations re- 

 garding the temperature of plants by the assistance of the ther- 

 mo-electric apparatus, I consulted M. Becquerel aboutthe mode 

 of employing this apparatus ; and he at once communicated to 

 me his manner of operating, with that frankness which charac- 

 terizes the true man of science. He informed me that, con- 

 jointly with M. de Mirbel, he had made the experiment, at 

 that time unpublished, of which an account N^as given in the 

 notice to which this is intended to reply, and that the result 

 of that experiment had been to enable him to discover in a 

 branch of a living tree which contained one of the soldered 

 points of the thermo-electric circuit, a temperature some de- 

 grees higher than that possessed by a dead branch which con- 

 tained the other soldered point, and wliich was estimated to 

 be of exactly the temperature of the atmosphere. If the result 

 of this experiment had been beyond the shadow of suspicion 

 of error, there would have been no doubt of Messrs Becquerel 

 and Mirbel having ascertained before me the existence of a 

 heat proper to the branches of plants, a heat long sought for 

 and at that time unsupported by evidence. I had doubts of 

 the certainty of the result. In the trunk and in the branches 

 of a tree, there is constantly Howing the ascending sap, which 



