430 Scientific Intelligence. 
happy distinction between the temperatures actually operative in vegeta- 
tion, and those which (being below the freezing point, dsc.) are altogether 
null for vegetation, and ought to be eliminated from the tables of mean 
temperature, when these are viewed in relation to the Northern and 
Southern geographical range of species. 
n 2, Geographical Botany, or the study of species, genera, and 
seed, whether affording facilities to dispersion or not. Chap. 8 considers 
the changes which may have taken place in the habitation of species, 
and discusses with great fullness the whole subject of naturalization, the 
obstacles in the way, the causes and means of transport, and the inter- 
changes which have been effected between the New and the Old Worlds. 
ble origin of the existing species; and brings 
far to prove the geological antiquity of the greater part of existing 
species ; and that their creation was probably successive. Chap. 12 treats 
: 2 a aE limits, the distribution of species within the area of the 
i 
* It is singular that M. De Candolle should be so slow to abandon the idea that the 
aborigines of Carolina, or any other part of North America cultivated or knew any- 
of the em which, if Raleig obtained them in Carolina, were certainly 1m- 
rted thi ut, though our aborigines had no potatoes, they had ipkine oF 
I ashes and beans, which all writers upon the hi , they farts 
overlooked, except the late Dr. Harris. e history of cultivated p have 
