252 Dr. J. D. Hooker on the Vegetation 
to the west of the American Cordillera and the Galapagos, or only to cross 
to the eastward on the lowest part of Mexico. 
Drymaria glaberrima. Verbena littoralis. 
Acacia Cavenia. | - - polystachya. 
Cassia picta. 4 Plantago tomentosa. 
Baccharis pilularis. Cryptocarpus pyriformis. 
Dictyocalyx Miersii. Boussingaultia baselloides. 
Clerodendron molle. Mariscus Mutisii. 
Again, these 120 are of such cominon occurrence over a large extent of 
coast, that their introduction into the Galapagos by causes now in operation 
can hardly be doubted. Presuming that such is the case, it may not be out of 
place to trace here the course of migration, the means by which it may have been 
effected, and the facilities for transport presented by the individual species. 
The position of the group between the Pacific Islands and America, points 
to these as the only mother-countries from which plants could have migrated. 
We have seen that many are common to the latter country ; but as at least 
15 species are also found in the South Sea Islands, it may be supposed that 
there has been migration from that quarter, especially as many plants are 
dispersed in a very remarkable manner over every group in the Pacific, esta- 
blishing themselves very soon after the formation of any new land, and whose 
further extension to the Galapagos might have been deemed possible *, 
There are 16 species found both in the Galapagos and South Sea Islands, 
whieh is nearly the half of what are common to the latter locality and 
America,—a very large proportion; but as they are unaccompanied by any 
- The species to which I allude as being so very prevalent over the tropical South Sea Islands, 
are ism 
Ozalis corniculata. Scevola Kenigii. 
Dodonea viscosa. Cordia orientalis, 
Lepidium piscidium. — Pisonia mitis. 
Tephrosia piscatoria. Achyranthes velutina. 
Guilandina Bonduc. Aleurites triloba. 
Sesuvium portulacastrum. Pandanus odoratissimus. 
Metrosideros polymorpha. . Cocos nucifera, 
Portulaca oleracea. Davallia solida. 
Adenostemma viscosum, Phymatodes vulgaris; 
together with several other Ferns, some Cyperacee and Graminee. 
