TEOPICAL 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 Labuan &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 



