CHAP. XIV ST. HELENA 307 



mainly African and especially South African, as indicated 

 by the presence of the genera Phylica, Pelargonium, 

 Mesembryanthemum, Oteospermum, and Wahlenbergia, 

 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 rano^e 

 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 sjDecific forms, 

 many of those found in the Miocene dejoosits of Switzer- 

 land, being hardly distinguishable from living species. 

 This shows, that identity of sjjecies of ferns between St. 

 Helena and distant countries does not necessarily imply a 

 recent origin. 



The Relation of the St. Helena Comiiositcc. — In an 

 elaborate j^ajoer on the Compositse,^ Mr. Bentham gives us 

 some valuable remarks on the affinities of the seven 

 endemic species belonging to the genera Commidendron, 

 Melanodendron, Petrobium, and Pisiadia, which forms so 

 important a portion of the existing flora of St. Helena. 

 He says : " Although nearer to Africa than to any other 

 continent, those composite denizens which bear evidence of 

 the greatest antiquity have their affinities for the most 

 part in South America, while the colonists of a more recent 

 character are South African." ..." Commidendron and 

 Melanodendron are among the woody Asteroid forms 

 exemplified in the Andine Diplostephium, and in the 

 Australian Olearia. Petrobium is one of three genera, 

 remains of a group probably of great antiquity, of which 

 the two others are Podanthus in Chile and Astemma in 

 the Andes. The Pisiadia is an endemic species of a genus 

 otherwise Mascarene or of Eastern Africa, presenting a 

 geographical connection analogous to that of the St. Helena 

 Melhanise,^ with the Mascarene Trochetia." 



Whenever such remote and singular cases of geo- 

 graphical affinity as the above are pointed out, the first 



^ "Notes on the Classification, History, and Geographical Distribution 

 of Compositce." — Journal of the Linnran Society, Vol. XIII. j). 563 (1873). 



- The Melhanioe comprise the two finest timber trees of St. Helena, now 

 almost extinct, the redwood and native ebony. 



X 2 



