212 DISENGAGEMENT OF HEAT. [BOOK n. 



morning falling back to nearly that of the surrounding air. 

 The maximum of elevation of temperature above that of the 

 atmosphere occurred 



On the 14th, at 3 P.M. 4'5 centigrade 

 15th, 4 P.M. 10 

 16th, 5 P.M. 10-2 

 17th, 5 P.M. 11 

 18th, 11 A.M. 8-2 

 19th, 10 A.M. 2-5 



These maxima might be almost compared to the access of 

 an intermittent fever. 



Vrolik and Vriese consider the so called Arum cordifolium 

 of the Isle of France to be the same as the aforesaid Colocasia 

 odora, upon whose temperature they made very numerous 

 hourly observations in the Botanical Garden of Amsterdam, 

 the result of which was, that the maximum of difference 

 observed between the temperature of the spadix and that of 

 the green-house amounted to 10 centig. (Ann. des Sc. 

 vol. v. 145.) Goppert adds that plants are generally warmer 

 than the air which surrounds them. ( Ueber warme Entwicke- 

 lung in der lebenden Pflanze. Wien, 1832.) 



That these phenomena should not be observed in ordinary 

 cases, is no proof that they do not also occur ; f6r it is easy 

 to comprehend that, when flowers are freely exposed to the 

 external air, the small amount of caloric which any one may 

 give off will be instantly dispersed in the surrounding air, 

 before the most delicate instrument can be sensible of it ; 

 and that it is in those instances only of large quantities of 

 flowers collected within a hollow case, like a spathe, which 

 prevents the heat escaping when evolved, that we can hope 

 to measure it. 



From experiments of Saussure, it seems certain that the 

 disengagement of heat, and, consequently, destruction of 

 oxygen, is chiefly caused by the action of the anthers, or at 

 least of the organs of fecundation, as appears from the fol- 

 lowing table : 



