of the Galapagos Archipelago. | 247 
form, thus: the more an island is indebted to a neighbouring continent for its 
vegetation, the more fragmentary does its flora appear, migration being effected 
by the transport of isolated individuals, generally in nowise related, while an 
independent flora is generally made up of groups, the lowest order of which 
we call genera. Hence the Coral Islands, whose flora is wholly borrowed, sel- 
dom have two species belonging to the same genus; as Keeling Island, for 
instance, on the west, and Malden Island to the eastward of the Pacific, in 
both of which the genera are to the species as 1:1; or the Society group, 
which presents so little novelty, and whose proportion of genera is as 1: 1°3. 
In the Sandwich Islands, on the other hand, our very imperfect materials givea 
proportion of 1:2; the Galapagos of 1: 1-7; and St. Helena about the same. 
In the abundance and peculiarity of Rubiacec, the Galapagos may be com- 
pared with the Sandwich group, which contain 18 species of this order unexcep- 
tionably peculiar, and all belonging to genera even confined to those islands. 
None of the Galapageian species belong to any but very common genera*. 
Of SoraANEz there are 13 species, a considerable number in proportion to 
the extent of the Flora, but almost the whole of them derived from the 
neighbouring coast. Only one, a species of Acnistus, is previously unde- 
scribed, except the Dictyocalyz, which is however a native of the shores of 
Peru. Solanum nigrum is the only flowering plant common to Great Britain 
and the Galapagos, except Verbena officinalis and Calystegia Soldanella; all 
are found in most intervening shores. 
The AuaRANTHACEZ are the only other family of flowering plants appearing 
to demand a particular notice, for their abundance and novelty are without a 
parallel in any tract of land of equal extent. "This is partly to be accounted 
for by their being partial to the immediate neighbourhood of the sea, but is 
more due to the position of the Galapagos being near to America, where, 
according to Martius, they attain their maximum. Littoral. and widely dif- 
fused as many plants of this order are, we do not find one of the ubiquitous 
species in this group; and indeed, except two belonging to the genus Ama- 
* In respect of Rubiacee, the vegetation of the Sandwich group has no analogy with that of any 
other islands. The Society Islands contain many more species, but all belonging to Asiatic genera. 
Even the specifically peculiar Rubiacee of St. Helena and Ascension have Cape congeners, and there 
is no genus of this order confined to Juan Fernandez. 
