CHAP. XIV.] 



ST. IIELENxA. 



295 



take possession of a country and occupy it almost to the complete 

 exclusion of later immigrants. The fact of so many European 

 "weeds having overrun New Zealand and temperate North 

 America may seem opposed to this statement, but it really is 

 not so. For in both these cases the native vegetation has first 

 been artificially removed by man and the ground cultivated ; 

 and there is no reason to believe that any similar effect would 

 be produced by the scattering of any amount of foreign seed 

 on ground already completely clothed with an indigenous 

 vegetation. We might therefore conclude a priori, that the 

 flora of such an island as St. Helena would be of an excessively 

 ancient type, preserving for us in a slightly modified form 

 examples of the vegetation of the globe at the time when 

 the island first rose above the ocean. Let us see then what 

 botanists tell us of its character and affinities. 



The truly indigenous flowering plants are about fifty in 

 number, besides twenty-six ferns. Forty of the former and ten 

 of the latter are absolutely peculiar to the island, and, as Sir 

 Joseph Hooker tells us, " with scarcely an exception, cannot 

 be regarded as very close specific allies of any other plants 

 at all. Seventeen of them belong to peculiar genera, and of 

 the others, all differ so markedly as species from their congeners, 

 that not one comes under the category of being an insular 

 form of a continental species." The aflinities of this flora are, 

 Sir Joseph Hooker thinks, mainly African and especially South 

 African, as indicated by the presence of the genera Phylica, 

 Pelargonium, Mesembryanthemum, Oteospermum, and Wahlen- 

 bergia, which are eminently characteristic of southern extra- 

 tropical Africa. The sixteen ferns which are not peculiar are 

 common either to Africa, India, or America, a wide range 

 sufficiently explained by the dust-like spores of ferns, capable 

 of being carried to unknown distances by the wind, and the 

 great stability of their generic and specific forms, many of those 

 found in the Miocene deposits of Switzerland being hardly 

 distinguishable from living species. This shows, that identity 

 of s;pecies of ferns between St. Helena and distant countries 

 does not necessarily imply a recent origin. 



The delation of the St. Helena Compositce. — In an elaborate 



