NIGER EXPEDITIOX. 129 
mainly, with certain of the more transportable classes of plants; 
and that the result must be, that the number of species belong- 
ing to each natural order would be great in proportion to the 
facility with which they bear transportation ; while only those 
Orders could be numerous, which possess that faculty in an 
eminent degree. But such are not the characteristics of the 
Mediterranean plants found in Madeira. 
On the other hand, the existence of such a continent, 
during the period when these islands bore the plants which 
they now produce, would argue the. former: presence of 
a very large Flora belonging to the type which now distin- 
guishes the islands in question from the Mediterranean, and 
of whose previous existence the remaining species, peculiar - 
to them, are the indication. Against this theory it might 
be urged, that more specific identity between the plants 
of the several insular groups, would:then be the natural 
consequence, than now is seen ; for the affinity of vegetation : 
between the different islands consists, not in identical species, _ 
but in representatives. The same agent, in short, which 
effected the peopling of the. several groups. with the plants — 
of continental Europe, would also have distributed more 
equally. the non-European species over the same area 
It is, however, to the lofty "n of. Atlas that. 
look, if any where, for. the. co 
A 
= Floras. Thus, we ^ expect to ) shoe 
= os Archipelago « on the higher ‘cae of the pce sid ad the e. 
; mountains of BE TÉ 'homz Fernanda: Po and the Cameroons, 
= = à partake ane Hamat 'egetation of a. i à 
E wena to cie low lands of the. adja ce: 
