369 
680. In the vegetable kingdom we have remarked 
(167.), that germinating seeds, when accumulated 
together, exhibit a sensible rise of temperature ; and 
in the process of malting, Dr Thomson has seen the 
radicles of barley, when kept without turning on the 
malt floor, shoot out half an inch in a single night, 
and the heat rise as high as 100 *. 
681. Many facts have been related (169.) in sup- 
port of the opinion that plants possess a power of 
producing heat. The experiments, however, of Mr 
Hunter, to shew that trees possess a temperature high- 
er than that of the surrounding air, are by no means 
satisfactory. He bored holes in trees to the depth of 
eleven inches, and found, that, in the month of 
March, when the atmosphere was 57.5, the thermo- 
meter in the tree stood at 55 only. In April, when 
the temperature of the air was 62, that of the tree' 
was only 56 j but when, on succeeding days, the 
air fell to 47, the tree then exceeded it in tempera- 
ture by eight degrees ; the day following, however, 
both the tree and the atmosphere were at 4-2. In 
October, when vegetation began to decline, and the 
temperature of the air was at 51.5, that of the tree 
was 55.5 ; and a few days afterwards, when the at- 
mosphere was at 47, the tree was from 5 to 6 warm- 
er. In November, a similar difference in tempera- 
ture was observed ; but in December, both the tree 
and air were found, in one experiment, to be exact- 
ly 29. In other instances, the temperature of the 
tree was sometimes higher and sometimes lower than 
Thomson's Svst, Chem. vol. v. p. 304. 4th edit. 
