CHAPTEK XXXII 



DARWINIAN INTERESTS 



THE special interest of 1866 was the discussion of Insular 

 Floras. As one of the crucial points of the great question of 

 Distribution, it had been a frequent subject of discussion in the, 

 correspondence with Darwin from the very first. Hooker now 

 chose this as the subject of an address before the British Asso- 

 ciation at Nottingham. In the course of the summer, while 

 the lecture was being prepared, the correspondence was very 

 full, and is largely quoted in M.L. i. 479 seq. 



Two hypotheses were in the field to account for the problem 

 involved one, the more obvious and sweeping, that of con- 

 tinental extensions ; the other, that of migration or accidental 

 transport. Darwin was a migrationist ; Forbes and others 

 pushed the extension theory to excess. In the then state of 

 knowledge, before the soundings taken on the Challenger expedi- 

 tion, which put unlimited extensionists out of court, Hooker 

 found either possible, but neither proved. The difficulties 

 were not all met by the arguments adduced, and in discussing 

 the subject he found himself without the stimulus of a thesis 

 to defend, or a side to take. 



' I think I know Origin by heart in relation to the subject,' 

 he tells Darwin ; and it was reading the * Origin ' that had 

 suggested questions as to ice-transport for European plants, 

 betokened by boulders in the Azores, and the European 

 character of the Madeiran birds. But while he deliberately 

 raised all the difficulties that would have to be overcome 

 by Darwin's arguments, he added : 



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