94 HEAT. 



88. Numerous observations were made upon this 

 subject, and it was shown that in order that much heat 

 should be evolved by the spadix of the Aroidese, a consi- 

 derable degree of vegetative vigour should be present in 

 the plant, and that in its native country the heat 

 evolved by the plant was much more considerable than 

 in our own. We have only room to remark on this in- 

 teresting subject, that the most valuable observations 

 have been recorded by Vrolick and Vriese ; they go to 

 prove that the evolution of heat by the spadix of Cala- 

 dium odorum is very considerable at certain periods of 

 the day, whilst at others, on the contrary, it is quite 

 unnoticeable ; (the maximum of the temperature showed 

 itself regularly between 2 and 4 in the afternoon ; whilst 

 in the experiments of Brogniart it occurred somewhat 

 later ;) and that the heat evolved also has its origin in the 

 spadix itself, and that the spatha or floral covering has 

 nothing to do with it. Goeppert has stated that the 

 seat of the evolution is to be looked for in the genera- 

 tive organs themselves, and that after the spadix had 

 been cut into five pieces, that portion on which the an- 

 thers were fixed showed a high degree of temperature 

 even at the expiration of eighteen hours. 



89. The evolution of heat in the flowers of plants is 

 not confined to the members of the family Aroidece, but 

 has been also noticed in many others : the male flowers 

 of a Cucurbita just opened, showed between 7 and 10 

 A.M. half a degree centigrade of heat more than the 

 external air ; and Bignonia radicans and Polyanthes 

 tuberosa, showed a difference between 0.3 and 0.5 

 cent, to the atmosphere. 



90. From the numerous experiments made upon 

 this subject, there can be no doubt of the actual evolu- 

 tion of warmth by plants, and that it is seen to very 

 great perfection in the region of the reproductive or- 

 gans ; that the changes taking place during the vegeta- 

 tion of the plant, as regards the union of oxygen with 

 carbon, are its main causes, (as seen likewise in the 



