xl INTRODUCTION. 
extent also this has been done for the subregions or secondary divisions; but it is 
obviously beyond the scope of the present sketch to pursue this to the end. Yet, 
without attempting to define secondary and further divisions of all the primary regions, 
it may be possible to give further particulars, which, with what has preceded, shall 
convey some general idea of the extensions of the characteristic types of the floras of 
these regions. . 
Wallace states that nothing like a perfect zoological division of the earth is possible ; 
and a perfect botanical division is equally impossible. Therefore the aim is a division 
that conveys in itself some notion of the extent of the dispersion of the characteristic 
types of each region. As already pointed out, it is obvious that a botanical division 
cannot be based on one class of plants, equivalent, if such could be found, to the 
Mammalia ; but rather on the general composition of the vegetation, and largely, too, 
apart from latitudinal position. On this plan it is not difficult to distinguish five 
primary regions; but if this number be exceeded, it must be doubled or trebled with a 
less satisfactory result. These five primary regions are :— 
1. Northern. 4, South American. 
2. African. 5. Australasian. 
3. Indian. 
These regions are unequal in extent, and the southern divisions are meridional rather 
than latitudinal; but the greater degree of differentiation of the vegetation justifies 
such a division; and a natural subdivision of the northern region, excluding the arctic 
zone, and, perhaps, the coldest arboreal zone, is in the same direction. But these five 
_ regions do not include quite all, because, for reasons given, the Sandwich-Island Flora 
cannot consistently be included in any one of them; and it would convey a false 
impression to rank this comparatively small, though highly peculiar Flora, as a 
primary region. Further, there isa remnant of an antarctic Flora which is scattered 
all round the hemisphere, constituting the coldest southern zone of vegetation. ‘These 
exceptional phanerogamic Floras will be separately discussed. 
An alternative primary division, which is more in accord with the writings of many 
botanists, and has some practical advantages over the one proposed, may be thus 
stated :— 
1. Northern Region. 
2. Neotropical Region. 3. Paleeotropical Region. 
4, Andine Region. 5. Cape Region. 6. Australasian Region. 
The anomalous Sandwich-Islands Flora and the fragmentary Antarctic Flora would 
be unattached in this, as in the foregoing plan. It is unnecessary to define these 
alternative regions, as their denominations are sufficiently descriptive to be intel- 
ligible. One of the advantages this division possesses over the one advocated, or rather 
the one point in which it radically differs, is the separation of the tropical and temperate 
