INSULAK FLORAS . 101 



ring in the Canaries and Azores, with unique genera, species 

 and varieties occurring on the outlying islets. This is the 

 wreck of an ancient flora, now surviving in Asia and America, 

 which is only found as fossil in Europe, having succumbed 

 to the Northern and Eastern floras that now hold that 

 continent. 



The Canaries, so much nearer to Africa, have not more than 

 a sprinkling of African plants ; nor have the Azores, so much 

 nearer America, more American plants than the others. The 

 tropical Cape de Verde Islands, while showing some affinities 

 with the Canaries and Madeira, have a mainly Saharan flora. 



Going further afield, the indigenous flora of St. Helena in 

 the isolation of the S. Atlantic, is mainly S. African. Linked 

 with this are the scanty plants of Ascension, though empha- 

 sising the effects of isolation. In the S. Indian Ocean, the 

 Kerguelen Land flora is clearly Fuegian, though the island 

 lies nearer to S. Africa and New Zealand than to S. America, 

 and its most notable plant, the Pringlea or Kerguelen Land 

 Cabbage, has no ally in the Southern hemisphere. 



Thus with all their peculiarities — the result, on Darwinian 

 principles, of isolation in survivals and modifications — no island 

 flora is an independent one. What was the link that made 

 immigration possible, whether ancient or recent ? This ques- 

 tion Hooker called ' the bete noire of botanists.' Now geology 

 did not favour extensions to the volcanic islands of the ocean : 

 the absence of land mammals and batrachians, and sundry 

 great gaps in the flora, also told against continental extension. 

 The difficulties of ocean transport in relation to prevailing 

 winds and currents, the vitality of seeds in sea-water or in the 

 crops of birds, or in mud sticking to their feet, the chances of 

 land insects reaching Oceanic islands x had been matter of 

 long discussion with Darwin. 



If he could pronounce for neither theory, still his balance of 

 opinion appears from his words : 



1 He writes to Dr. Cunningham (see p. 80), May 18, 1867 : ' Your observa- 

 tions on the abundance of terrestrial insects seen so far out at sea alive are 

 very curious. Pray collect all such evidence carefully and collate it, it 

 bears so strongly on Darwin's theory of populating Oceanic Islands from 

 Continents.'' 



