372 FREAKS OF PLANT LIFE. 



temperature of 72°, though the main portion, which is 

 subterranean, is surrounded by a soil heated between 

 90" and 100°, is remarkable, and is no doubt proxi- 

 mately due to the rapidity of evaporation from the 

 foliage, and consequent activity of the circulation. 

 Its exposed leaves maintained a temperature of 80'^, 

 nearly 25° lower than the similarly exposed sand and 

 alluvium." The inference is, that the liquids taken 

 up by the roots, being at the degree of heat which 

 the soil possesses, at that depth tends to warm the 

 tree in the cold season, and to cool it, in comparison 

 with the air, in the warm season. 



Apart from this question of general temperature 

 we are concerned chiefly with the great increase of 

 heat evolved by plants under certain conditions, 

 especially at germination, and during flowering. 

 That is, the phenomena of increased temperature 

 under special circumstances. In animals the heat of 

 the body is maintained by a process analogous to 

 combustion. Oxygen combines with carbon and 

 forms carbonic acid, which latter is thrown off, the 

 change or oxidation being accompanied by the 

 evolution of heat. As it is in the combustion of 

 carbon so is it in the conversion of carbon in the 

 animal body, and so also in plants, under special 

 conditions, when oxidation is greatly increased heat 

 is evolved, chemical changes take place, and the 

 burning log, the breathing animal, and germinating 



