354 



C. SKOTTSBERG 



is considerably dififerent; thus it may be argued that "the birds and plants do 

 not come under the same category". Darwix replied that 



the migration of birds is continuous and frequent, and the individuals surviving and 

 breeding, they keep up the specific type, and do not give origin to local varieties; 

 whilst the transport of seeds is casual and rare, and very few surviving, these not being 

 crossed by the original stock, in the process of time give rise to varieties, etc., and 

 do not perpetuate the continental races (p. lo). 



This is the situation in a nut-shell, and Darwin's arguments are repeated by 

 scores of biogeographers to this very day. 



Also St. Helena, Ascension and Kerguelen made HoOKER hesitate: 



They [St. Helena and Ascension] have no land birds, but an African vegetation ; 

 and though nearly midway between Africa and America, they have scarcely a single 

 American type of flowering plants, and Kerguelen's Land has a flora of whose ele- 

 ments most have emigrated not from the nearest land, but from the most distant (p. lo). 



Hemslev [i2y. 59) remarks that HOOKER seems to have forgotten the 

 Compositae in St. Helena, most of them showing American affinity. 



Kerguelen's nearest land is Antarctica, but not a single flowering plant is 

 known from the coast south of Kerguelen. Africa as a mother country — it goes 

 without saying that subtropical or warm temperate plants cannot endure a 

 subantarctic climate, and only the most distant lands, Tierra del Fuego and the 

 Falkland Islands, were, thanks to the strong and constant west wind drift, re- 

 garded as a mother country. Even if South Georgia served as an intermediate 

 station, the distances are very great; besides, we do not look west for the an- 

 cestors of the peculiar endemics in the Kerguelen area. Where the capacity of 

 the dispersal agents appeared to be inadequate, HOOKER was strongly inclined 

 to look for better land connections. The existence of identical Macaronesian 

 species on Madeira and the Canary Islands can, he says, hardly be explained 

 without the help of 



intermediate masses of land, as the Salvages (supposing them to have been larger) . . . 

 the only conceivable means of interisland transport . . . and if intermediate islands are 

 granted (and Mr. Darwin freely admits these), why not continents? 



He must have found that the distance between Madeira and the Canaries is too 

 large to permit direct transport of diaspores under present wind and current 

 conditions; in the Kerguelen case they are, at least, favourable. Nevertheless, 

 later on HoOKER's faith in transoceanic migration was not as steadfast as before; 

 the case of Kerguelen troubled him ( ? ?^) : 



Turning to the natural agents of dispersion, winds are no doubt the most power- 

 ful, and sufficient to account for the transport of Cryptogamic spores; these, almost 

 throughout the year, blow from Fuegia to Kerguelen Island, and in the opposite 

 direction only tor very short periods, but appear quite insufficient to transport seeds 

 over 4000 miles (p. 13). 



Various phenomenons . . . common to . . . Kerguelen, the Crozets and Marion, 

 favour the supposition of these all having been peopled with land plants from South 

 America by intermediate tracts of land that have now disappeared; in other words, 



