250 Dr. J. D. Hooxer on the Vegetation 
the species and genera of those orders contained in one group of islands having 
little or no relation with those of the others. . 2ndly, That the chief points of 
difference are explicable, and owing chiefly to the relations the islands bear to 
the nearest continents, and to the nature of the soil and climate, &c.; such 
are the absence of Ferns, and the peculiar forms of Composite and Rubiacee, 
and other orders having their nearest allies on the neighbouring continents. 
3rdly, The smallest amount of novelty will be found amongst the more per- 
fect plants, if such be so considered as possess a double floral envelope and 
polypetalous corolla, including the Thalamiflore and Leguminose, whilst the 
greatest amount of new species exists in the lower orders, as Amaranthacee 
and Piperacew, or in the incomplete genera of Euphorbiacee, and in the 
Composita. On the other hand, there are somewhat fewer peculiar and new 
plants amongst the Monocotyledones than the Dicotyledones; and the amount 
of novelty amongst the Ferns is small in comparison to the higher orders. 
II. In this second part of the essay I propose to treat of the Flora of the 
Galapagos as divisible into two types: these are the West Indian (including 
Panama), to which the plants common to other countries and. the dubious 
species almost universally belong; and the Mexican and temperate American 
type, or that under which the great majority of the peculiar species will rank. 
Those which I have called dubious species consist of a few plants which more 
properly belong to neither of these divisions, including àll such as are so 
nearly allied to continental forms as to appear scarcely distinguishable specifi- 
cally, or if distinguishable, dependent on characters which, though sufficiently 
obvious, are extremely liable to variation; such are possibly altered. forms of 
introduced species, dependent on the combination of circumstances which they 
are exposed to in the Galapagos for the appearances they assume: such plants 
are noticed in the descriptions given of the species, and it is sufficient to state 
here, that they nearly all belong to the West Intlian type. 
The species which I have referred to the Mexican type (from the affinities of 
the remarkable Composite) include those whose nearest allies belong to Mexico 
or the higher levels in Columbia, or to the lower latitudes of the Southern 
United States, California or Chili; unlike those of the West Indian type, they 
are all specifically entirely distinct from their continental congeners, and are 
about 45 in number, belonging to such genera as Discaria, Dalea, Phaca, 
