SPECIFIC! TEMPERATURE OF TREES. 
157 
certain amount of weight is to be ascribed to this element, in 
estimating tlie action of the forest upon atmospheric temper¬ 
ature. 
“ Observation shows,” says Meguscher, “ that the wood of 
a living tree maintains a temperature of + 12° or 13° Cent. 
[= 54°, 56° Fahr.] when the temperature of the air stands at 
3°, 7°, and 8° [= 37°, 46°, 47° F.] above zero, and that the 
internal warmth of the tree does not rise and fall in proportion 
to that of the atmosphere. So long as the latter is below 18° 
[= 67° Fahr.], that of the tree is always the highest; hut if the 
temperature of the air rises to 18°, that of the vegetable growth 
is the lowest. Since, then, trees maintain at all seasons a con¬ 
stant mean temperature of 12° [= 54° Fahr.], it is easy to see 
why the air in contact with the forest must be warmer in win¬ 
ter, cooler in summer, than in situations where it is deprived 
of that influence.” * 
Boussingault remarks: “ In many flowers there has been 
observed a very considerable evolution of heat, at the approach 
of fecundation. In certain arums the temperature rises to 40° 
or 50° Cent. [= 104° or 122° Fahr.]. It is very probable that 
this phenomenon is general, and varies only in the intensity 
with which it is manifested.” f 
If we suppose the fecundation of the flowers of forest trees 
to be attended with a tenth only of this calorific power, they 
could not fail to exert an important influence on the warmth 
of the atmospheric strata in contact with them. 
In a paper on Meteorology by Professor Henry, published 
in the United States Patent Office Report for 1857, p. 504, 
that distinguished physicist observes: “ As a general deduc¬ 
tion from chemical and mechanical principles, we think no 
change of temperature is ever produced where the actions 
belonging to one. or both of these principles are not present. 
Hence, in midwinter, when all vegetable functions are dor¬ 
mant, we do not believe that any heat is developed by a tree, 
or that its interior differs in temperature from its exterior 
* Memoria mi JBoschi di Lombardia, p. 45. t Economic Rurale, i, p. 22. 
