480 GEOGRAPHICAL DISTRIBUTION [CHAP. VI 



Letter 365 your writing, you would like to hear my notions. I cannot 

 admit the Atlantis 1 connecting Madeira and Canary Islands 

 without the strongest evidence, and all on that side : the 

 depth is so great ; there is nothing geologically in the 

 islands favouring the belief ; there are no endemic mammals 

 or batrachians. Did not Bunbury show that some Orders of 

 plants were singularly deficient? But I rely chiefly on the 

 large amount of specific distinction in the insects and land- 

 shells of P. Santo and Madeira : surely Canary and Madeira 

 could not have been connected, if Madeira and P. Santo had 

 long been distinct If you admit Atlantis, I think you are 

 bound to admit or explain the difficulties. 



With respect to cold temperate plants in Madeira, I, of 

 course, know not enough to form an opinion ; but, admitting 

 Atlantis, I can see their rarity is a great difficulty ; otherwise, 

 seeing that the latitude is only a little north of the Persian 

 Gulf, and seeing the long sea-transport for seeds, the rarity of 

 northern plants does not seem to me difficult. The immigra- 

 tion may have been from a southerly direction, and it seems 

 that some few African as well as coldish plants are common 

 to the mountains to the south. 



Believing in occasional transport, I cannot feel so much 

 surprise at there being a good deal in common to Madeira 

 and Canary, these being the nearest points of land to each 

 other. It is quite new and very interesting to me what you 

 say about the endemic plants being in so large a proportion 

 rare species. From the greater size of the workshop (i.e., 

 greater competition and greater number of individuals, etc.) 



1 Sir J. D. Hooker lectured on " Insular Floras" at the Nottingham 

 meeting of the British Association on Aug. 27th, 1866. His lecture is 

 given in the Gardeners' Chronicle, 1867, p. 6. No doubt he was at this 

 time preparing his remarks on continental extension, which take the 

 form of a judicial statement, giving the arguments and difficulties on 

 both sides. He sums up against continental extension, which, he says, 

 accounts for everything and explains nothing ; " whilst the hypothesis 

 of trans-oceanic migration, though it leaves a multitude of facts un- 

 explained, offers a rational solution of many of the most puzzling 

 phenomena." In his lecture, Sir Joseph wrote that in ascending the 

 mountains in Madeira there is but little replacement of lowland species 

 by those of a higher northern latitude. " Plants become fewer and fewer 

 as we ascend, and their places are not taken by boreal ones, or by 

 but very few." 



