IV.-CONTRIBUTIONS TOWARDS THE BOTANY OF 



ASCENSION. 1 



By R. N. RUDMOSE BROWN, D.Sc., University of Sheffield. 



ON the return of the Scottish National Antarctic Expedition from Cape Town to 

 Scotland, the Scotia spent a few days at the island of Ascension (7 55' S., 14 25' W.), 

 and I was enabled to make some observations and collections of botanical interest. 

 While the earliest record of the flora of this island dates from some two centuries ago, 

 and although it has been visited by botanists at intervals since, including Joseph D. 

 Hooker in 1843, the first really comprehensive collections brought back were those 

 made by H. N. Moseley, during the visit of the CJiallenger in 1876 ; in 1876 the 

 German Transit of Venus Expedition in the Gazelle made a call at the island, and 

 Dr Naumann collected a number of cryptogams. The results of all these expeditions 

 are fully summarised in Mr W. Bottiug Hemsley's exhaustive work on insular floras, 2 

 which, despite the fact of its having been published in 1885, practically includes all 

 our knowledge of the flora of Ascension until the visit of the Scotia in 1904. 3 The 

 island comprises an area of some forty square miles of undulating plains lying around 

 the base of Green Mountain, a Tertiary volcano which rises to a height of 2840 feet. 



The geological constitution of the island is hard volcanic slag and some beds of 

 volcanic ashes. 4 With the extreme dryness of the atmosphere, the want of rain, and 

 the equability of temperature at sea-level, the low-lying ground remains almost as 

 fresh and unweathered to-day as if its formation was a matter of only a few years ago 

 instead of ages. The vegetation of these dry and soil-less plains is naturally very scanty; 

 in fact, save in some exceptionally favoured spots, they are practically a desert : but 

 that want of water is the one vital hindrance to vegetation is more clearly seen as one 

 ascends Green Mountain. The geological structure and soil of this old volcano is, of 

 course, essentially the same as that of the plains, but the vegetation steadily increases 

 from the foot upwards until before 2000 feet one is pleasantly surprised to find oneself 

 amidst a veritable oasis of rich sub-tropical vegetation. Still higher the vegetation 

 assumes a more temperate aspect, and the top, exposed to the continually blowing 



1 Reprinted with slight alterations from Trims. andProc.Bot. Soc. Edin., xxiii., 1906, pp. 199-204. 



2 Report on the Voyage of H. M.S. " Challenger," 1873-76: Botany, W. 13. Hemsley, i. n. p. 31 el seq. 



3 The German Antarctic ship Gauss called at Ascension in 1903, and made a small collection, which included 

 no phanerogams. See Deutsche Siidpolar-Exp. (1901-03), Bd. viii. 1906. 



4 For a fuller account of the geology of Ascension, see Darwin's Naturalist's Voyage. 



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