HEAT OF VEGETABLES. 89 



been attributed to their being budded on a 

 Pomegranate stock, of which I have never 

 been able to obtain the smallest confirma- 

 tion. 



Heat can scarcely be denominated a secre- 

 tion, and yet is undoubtedly a production, 

 of the vegetable as well as animal body, 

 though in a much lower degree in the former 

 than the latter. The heat of plants is evinced 

 by the more speedy melting of snow when 

 in contact with their leaves or stems, com- 

 pared with what is lodged upon dead sub- 

 stances, provided the preceding frost lias 

 been sufficiently permanent to cool those sub- 

 stances thoroughly. Mr. Hunter appears to 

 have detected this heat by a thermometer 

 applied in frosty weather to the internal parts 

 of vegetables newly opened. It is evident 

 that a certain appropriate portion of heat is a 

 necessary stimulus to the constitution of every 

 plant, without which its living principle is 

 destroyed. Most tropical plants are as effec- 

 tually killed by a freezing degree of cold, as 

 by a boiling heat, and have nearly the same ap- 

 pearance, which is exemplified every autumn 

 in the Garden Nasturtium, Trapaolum ma* 



