of the Galapagos Archipelago. 24$ 



to which I shall allude, is the gummy exudation for which the shrubby Sca- 

 lesice are conspicuous, and which is equally a characteristic of some of the 

 St. Helena Compositce. The species in both instances are inhabitants of arid 

 spots, fully exposed to the sun of the torrid zone, which together seem favour- 

 able to the copious secretion of gums and gum-resins in various parts of the 

 world. 



LEGUMiNosiE. — This order is second only to the last in number of species, 

 of which there are 24 contained in the various collections, but differs con- 

 spicuously in its proportion of novelty, there being no peculiar genus, and 

 only 7 species which are not found on the adjacent continent. Of all the large 

 natural orders of flowering plants, the Leguminosce contain by far the largest 

 amount of universally diffused species, including very many of the littoral weeds 

 of the tropics. Observation proves that this is in a great measure due to the 

 transporting power of water, for neither do the seeds of the dispersed species 

 bear winged appendages, nor are they of such a size as renders it probable 

 that they are carried by aerial currents. The ubiquitous species possess, on 

 the other hand, remarkable powers of resisting the effects of time and ex- 

 posure, besides a vegetative power that enables them to overcome obstacles 

 in the soil and climate of the locality they are transported to ; qualities which 

 the Compositce probably possess in a very limited degree, for we see their 

 feathery pappus to have had little effect in spreading the majority of the 

 individual species beyond any but very narrow limits. 



Of the Galapageian genera only Dalea and Galactia are exclusively Ame- 

 rican, and all but the 7 species mentioned above are common tropical species, 

 particularly in the West Indian islands. 



EuPHORBiACEiE form a very large proportion of the Galapageian Flora, 

 consisting of 18 species, included in the tropical genera Acalypha, Croton, 

 Euphorbia and Phyllanthus. They form ^ of the Phsenogamia, very much 

 exceeding the proportion for the tropics of the new world, which is stated by 

 Baron Humboldt as ^, or of Western Africa, which Mr. Brown gives as -^. 

 In amount of peculiar species this order here ranks next to Compositce, f of 

 the whole belonging to species very distinct from those of other countries ; 

 the remainder are common West Indian or Southern United States plants. 



In the prevalence of peculiar Euphorbiacece and Rubiaceae, this group has 



2 k2 



