246 Dr. J. D. Hooxer on the Ve egetation 
features in common with the similarly barren island of Ascension, where 
almost the only Dicotyledonous plants are one of Rubiacee and a prostrate 
Euphorbia, allied to, and of the same habit as, the Galapageian — The 
Aristida too of Ascension, which is there the only abundant grass, is repre- 
sented here by two congeners which occupy similar situations. This feeble 
though decided analogy existing between the vegetation of arid volcanic islets 
in opposite oceans is very singular, and is a feature analogically repeated as 
it were by the two moister islands of Juan Fernandez and St. Helena, which 
possess very similar and closely-allied peculiar forms of Wahlenbergia. 
The shrubby Crotons of this group are no doubt conspicuous features in 
the vegetation ; the other species of the order are mere weeds. 
Rusiacez.—An order largely represented, including upwards of 41- of the 
flowering plants, whilst of the tropical Flora of the neighbouring continent 
they form but 5, and of that of the whole globe 4. "The amount of 
peculiarity is also very large, though (as in Euphorbiacee) the new species are 
found under a very few genera; in this case 11 of the 15 are such, belong- 
ing to three genera, of which one, Borreria, alone contains 8. "This last and 
Euphorbia contain. the. majority of the weeds of the Galapagos, and are 
farther the two largest Pheenogamic genera in the group. 
[t is singular to remark to what different genera of plants various islands 
are indebted for their greatest peculiarity, and how often it is the case that 
such genera give a character of individuality to the scenery. This is effected 
in the Galapagos by covering the lower lands with Euphorbia and Borreria, 
whilst the large genera Scalesia, Croton and Cordia give the conspicuous fea- 
tures of the vegetation of the higher regions. In like manner in Juan Fernan- 
dez and St. Helena the most conspicuous, which are also the largest genera, 
are of Composite and Campanulacee ; and in the Sandwich Islands Goodeniacece 
and Lobeliacec ; while in the Society group; on the other hand, out of upwards 
of 200 genera; Piper is the only one containing as many as 3 peculiar species. 
This leads me to another. remark, that the greater the amount of peculiarity 
an insular flora presents; the closer relationship do the Species it contaitis 
bear to one another. This is best shown by observing the proportion that 
pa: Species bear to the genera, which more frequently contain several species 
in the peculiar than in the borrowed. floras. This may be stated. in another 
i; 
A 
