136 A NATURALIST ON THE "CHALLENGER." 



Cardamine Mrsuta, Nertera depressa, Empetrun nigrum var. 

 rubrum, Lagenophora Commersoniana, and Apium australe ; 

 and the flora contains besides the strictly American genus 

 Chevreidia" 



The close similarity of the flora of the three islands of the 

 group points to a former connection between them. Their high 

 cliffs, composed of successive layers of lava, and the absence, 

 except in Tristan da Cunha, of well marked centres of eruption, 

 as well as their general features, show that they have undergone 

 great denudation. A sounding between Tristan da Cunha and 

 Inaccessible Island gave a depth of 1,000 fathoms ; between 

 Inaccessible and Nightingale Islands, the depth was 460 

 fathoms. 



It is obvious, from the relative position of the three islands, 

 that the prevalent winds blow directly from Inaccessible Island 

 towards Nightingale Island and Tristan da Cunha. 



With regard to the Cryptogamous vegetation of the group, 

 nearly all the seaweeds, as appears from Prof. Dickie's report on 

 the specimens collected by me, are Cape of Good Hope species, 

 or occur at the Cape as well as at numerous other localities ; two 

 only are new and apparently endemic. Of Fungi, an Agaricus, 

 which grows on the Phylica stems, is described by Mr. Berkeley 

 as new, as A. phylicigena. Of the mosses and Hepaticce, Mr. Mitten 

 describes ten species as new, out of thirty-six collected by me ; 

 of eleven lichens collected, two were new ; one, Lecanora acun- 

 hana, is noted by Nylander as " bene distincta." 



An Islander told me that the flowering plants on Gough 

 Island were the same as those of Tristan da Cunha, but he 

 thought there were different ferns ;■ he had lived there some 

 time sealing. 



Scientific Notices of the Tristan da Cunha Group. 



Du Petit Thouars, flora of the island, in his "Melanges." 



Captain Carmichael's account of the island in " Linn. Trans.," Vol XII, 

 p. 496. 



For descriptions of the collections of plants made by me in the Islands, 

 see list of papers relating to the "Challenger" Expedition, at the end of this 

 Book. 



For a description of Gallinula nesiotis, by P. L. Sclater, F.R.S., &c, see 

 "Proc. Zool. Soc, 1855," p. 146. 



