of the Galapagos Archipelago. 253 



Polynesian species not found in America, it is perhaps the more probable that 

 they migrated from the eastward into the Galapagos*. 



The means of transport which may have introduced these plants are, oceanic 

 and aerial currents, the passage of birds, and man. 



To the first of these divisions the majority of the littoral species may be 

 referred ; they are about 20 in number, chiefly such as are common to most 

 warm latitudes, as : — 



Cissampelos Pareira. Avicennia tomentosa. 



Tribulus cistoides. Scavola Plumieri, 



Tephrosia littoralis. IpomcBa maritima. 



Rhizophora Mangle, Calystegia Soldanella. 



Verbena littoralis. Heliotropium Curassavicum. 



To the non-littoral species, also possibly introduced by marine currents, 

 belong the greater part of the remaining Leguminosce, the Boraginece, f^erbe- 

 nacece and Solanece. These and the above have seeds too large for probable 

 transport by winds ; they possess no means of attaching themselves to birds, 

 &c., whilst the indurated seed-coats of some, and the exalbuminous embryos of 

 many, probably aid them in resisting for some time the effects of salt water. 



It is only such species as have small seeds, or in which these are furnished 

 with wings or other appendages, that offer aids to the transport by winds ; 

 they are few in number: such are Gossypium, Baccharis and Ageratum, the 

 caryopsides of which last are, singularly enough, in this group only deprived of 

 pappus. Lobelia Xalapensis, Scoparia dulcis and the Urticece have very small 

 seeds. 



That birds are active agents in transporting species may be presumed from 



* The more clearly to show the discrepancy between the Floras of the Pacific and Galapagos, I may 

 mention that I have examined that of Maiden Island, the nearest of the Tropical Polynesian Islands 

 to the Galapagos. Most of its species are very abundant over all the tropical South Sea Islands, and 

 none are absolutely peculiar : they are, \. Phymatodes vulgaris; 2. Davallia solida ; 3. Eragrostis, ap.; 

 4. Guettarda, sp. ; 5. Euphorbia ramosissima ; 6. Achyranthes velutina ; 7. Boerhaavia ; 8. Lepidium pisci- 

 dium; 9.Sida; 10. Oxalis corniculata; 11 . Tribulus cistoides ; 12. Crotalaria; 13. Portulaca; 14. Talinum 

 patens; 15. Coprosma, sp. ; of which only the Tribulus, and perhaps the Portulaca, are Galapageian, 

 whilst even the Ferns and 8 of the 15 genera are not so. This, coupled with the fact stated above, 

 that there is no species an inhabitant of the Galapagos and the old world, that is not equally found 

 in the new, are conclusive against the probability of any direct migration from the westward. 



2 l2 



