G8 HEAT OF VEGETABLES. 



which, on a black currant stock, is, as far as I can 

 learn, without any foundation, and is indeed at the 

 first sight absurd. I have known the experiment tried 

 to no purpose. The rose vulgarly reported to be so 

 produced is merely a dark Double Velvet Rose, a 

 variety, as we presume, of Rosa centifolia. Another 

 report of the same kind has been raised concerning 

 the Maltese Oranges, whose red juice has been attri- 

 buted to their being budded on a Pomegranate stock, 

 of which I have never been able to obtain the smallest 

 confirmation. 



Heat can scarcely be denominated a secretion, 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 steins, compared with 

 what is lodged upon dead substances, provided the 

 preceding frost has been sufficiently permanent to cool 

 those substances 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 por- 

 tion of heat is a necessary stimulus to the constitution 

 of every plant, without which its living principle is 

 destroyed. Most tropical plants are as effectually killed 

 by a freezing degree of cold, as by a boiling heat, and 

 have nearly the same appearance; which is exemplified 

 every autumn in the Garden Nasturtium, Tropaolum 



