Vol. I] STEWART— BOTANY OF THE GALAPAGOS ISLANDS 211 



the same islands. In the first instance it seems likely that the 

 size of the island and the degree of slope are involved. On 

 large islands, like Albemarle and Indefatigable, the southern 

 sides slope very gradually, and the transition and moist regions 

 extend down much lower than on Abingdon and James, which 

 are smaller and have steeper sides. A notable exception 

 occurs, however, at Iguana Cove on the southwest side of Albe- 

 marle Island, where the conditions are very peculiar indeed. 

 This is the only place on the islands, outside of a few isolated 

 spots near brackish springs, where there is sujfficient moisture 

 at sea level to support a mesophytic vegetation. But the extent 

 of the moist region at this place is very limited, for at Christo- 

 pher Point, only five miles north, and at Essex Point, four 

 miles south, the vegetation at sea level is again very xero- 

 phytic. The great difference in elevation of the different 

 regions on the leeward and windward sides of the islands, is 

 due to the fact that the fog in passing over the tops of the 

 mountains rolls down but a short distance on the leeward sides, 

 and leaves the islands at a much higher level than it struck 

 them on the windward sides. The lower limits of the moist 

 regions are usually as well marked, by the difference in the 

 color of the vegetation, on the leeward as on the windward 

 slopes of the islands. 



General Features of the Flora 



pteridophyta 



Filices are the family that contains the largest number of 

 species, but at the same time the smallest number of endemic 

 forms in proportion to the number of species represented, of 

 any family of vascular plants found on the islands. Ferns 

 occur mostly in the transition and moist regions, where they 

 sometimes grow in great profusion. They are not confined to 

 these regions, however, as there are instances of their occur- 

 rence under decidedly xerophytic conditions in the dry region. 

 The species which occur thus are Ceropteris tartarea, Cheilan- 

 thes micro phylla, Notholaena sulphur ea, Poly podium squam- 

 atum, and Trachypteris pinnata. Hydrophytic ferns are few 

 in number, and are confined to a few rather restricted areas, 

 in the moist regions on several islands, where the amount of 



