TKOPICAL COOLING 29 



I wish I could see any way of ' ingenious wriggling ' that 

 would remove the crushing evidence in the shape of tropical 

 forms against tropical cold. You have no idea of the 

 magnitude of such a case as the Dipterocarpeae, a Nat. Ord., 

 not a mere genus, of 10 genera and 112 species all from 

 Ceylon, the Malayan Peninsula and Islands and of which 

 a good 100 more species and many more genera are still 

 to come from Borneo, Sumatra &c. All are woody, and far 

 the larger proportion are large timber trees not one ascends 

 at all to any height and analogous species to living are 

 found in tertiary coal-beds of Labuah &c. 



Darwin's appreciation of this Essay is recorded in his 

 letter of February 25. (M.L. i. 465 et seq.) ' Such papers,' 

 he exclaims, ' are the real engine to compel people to reflect 

 on modification of species ' : and ' What a splendid new and 

 original evidence and case is that of Greenland.' 

 To this Hooker replies on the 27th : 



I am greatly pleased and indeed relieved by your letter, 

 for no one but Oliver (who can judge) has pronounced any 

 opinion on my Greenland paper, and I find that one is so 

 easily deceived as to the value of such researches that I was 

 anything but sanguine of your approval. 



In a subsequent letter (March 3) he refers to certain correc- 

 tions which had not been put into the final proofs errors 

 which required the eye of Darwin to detect and replies to 

 several questions raised by Darwin. 



I am really sorry about the blunders in my Arctic paper 

 (and, in anticipation, for the others you will find); but it is 

 of mighty little consequence, you being the only one who 

 has found it out ; it is well this should be so, I should never 

 have written such papers but for you ; and the evulgation 

 of your views is the purest pleasure I derive from them. 



I am staggered equally with you by the idea that Green- 

 land ought to have been depopulated during the Glacial 

 period ; but if so, how is it that its temperate flora is no 

 richer than its arctic if it had been populated by migration 

 since the Glacial Epoch, surely some species suited to the 

 south end would have got over there there are plenty such 



