THE REGIONS OF VEGETATION. 317 
Regions are subdivisions of provinces, and vary in number 
in each, according to cireumstances. "The chief object is to 
constitute them on the largest assemblage of natural features, 
and be occasionally guided by general character as well as 
minute details. For several reasons it is sufficient that they 
possess a certain number of peculiar species, without any re- 
lation to corresponding genera or families. First—In two 
analogous regions of different hemispheres, or continents, there 
may be a very close resemblance among the genera, when 
nearly the whole of the species are peculiar. Second—In 
mountain ranges it is unusual to find peculiar genera, yet a 
great number of the species may be so, and several of these 
chains have every claim to be considered distinct regions. 
Third—It must be remembered that genera are often artificial 
assemblages, and that a safer course is pursued by directing 
our attention to species. "The general appearance and nature 
of the vegetation are important, whether consisting of forest, or 
of low bushy plants, or of herbaceous kinds, or of sandy plains 
and their appropriate plants. Negative circumstances have 
also their weight, as the absence of trees in particular regions ; 
also the non-existence of Aeaths in America, and Cacftee in 
Asia and Africa. "The presence or absence of a plant may 
assist in determining geographic relations ; thus Erica vulgaris 
is indigenous in Greenland, which renders it more natural to 
assign this country to Europe than to America which has no 
heaths, 
When the regions are once satisfactorily established, it 
would be desirable that all floras should be defined by them, 
instead of the present injudicious method by which they 
are too often circumscribed within political boundaries. Each 
flora might then advance separately to perfection, and the 
ample details which should accompany it would include a 
complete account of a particular state of vegetation. The 
local vegetation of the whole world would be contained within 
a definite compass, research be greatly facilitated, and the 
references of travellers much lightened. 
Whilst endeavouring to sketch an outline of those regions 
