WCP2492

[1]¹

30.1.11

Dear Mr Wallace,

When you kindly sent me the 'The World of Life'² you did me the honour to ask for my frank opinions.

Take these frankly. I think it is a very remarkable book. I do not know which to admire most the the extent of the ground covered, or the vivacity, resourceful knowledge and unflagging interest with which it is handled.

There are many important matters discussed in it on which our convictions diverged: on these I shall not touch.

What you have said on plant distribution is admirable. It must have cost you a immense amount of labour. It will be very helpful to me in a small book I hope some day to write.

If we [illeg.] the known families of flowering [2] plants at 240, the [illeg.] almost exactly 2/3. I do not see myself in this the result of a high temperature and moisture (p. 28). But I agree with my friend C. de Candolle³ that vegetation is an essentially intertropical phenomenon, which we only see in temperate regions 'virtes affabilis'.

The fact that in the northern hemisphere a small area will often contain a larger proportion of the species & an extensive one is certainly true. The area of Kew is some 1/2 a sq. mile and much of the surface has never been cultivated.

When I was young I was very much interested in Mrs. Merrifield's⁴ 'Natural History of Brighton'⁵ which attempted a more or less complete account of the Fauna [3] and Flora in a limited area. I attempted the same thing for Kew and published the result. But it has hardly received any notice. The wild flowering plants are 422 rather more than H. C. Watson⁶ got on a square mile in Thames Ditton.

My explanation is that the northern flora are not poor and not very ancient and that the competition in consequence ^{has not been} is not very severe.

That flora increases in richness as we go south seemed to me to follow necessarily from the preponderence of land in the northern hemisphere

You seem to think (p. 32) that the Cape Flora had formerly an extension in the Indian ocean. That is arguable. But I prefer to see it as the last refuge of a high level flora which once reached to Abyssina in the E. & the Cameroon in the W.

I am familiar with the facts about Penang as I sent Curtis⁷ there and hardly a [4] year passed that he did not send me some new [illeg.] from the very limited bit of forest that his [illeg.] alone enabled him to examine.

I entirely agree with you (p. 20) that seeds are adapted for short dispersal and that distant transmission is, so to speak, merely incidental.

Notwithstanding their large-winged fruits. the Dipteraceae do not seem capable of dist transmission for more than very short distances (p. 91); in fact the seeds often germinate on the tree. The species are in consequence apt to be gregarious. But I did find amongst the Challenger [illeg.] seeds some belonging to Dipteraceae as it happened they belonged to a genus in which the fruit had no wings. I rather think I [sic] was the fruit to [2 words illeg.] from New Guinea.

I have long seen that, botanically, 'Wallace's line' must be moved Eastward. [5] I cannot account for the [illeg.] of the Flora of W. Australia, except great antiquity and possibly the desiccation of the interior. But the fact is understood. My son⁸is an engineer but no botanist. I induced him, when out there but much occupied, to make me a small collection. It contained a large proportion of novelty and several new genera.

We ought to have been able to give you some facts from Kew about the Flora of Tropical Africa. I think you understate its richness. We shall be better able to judge when the Flora I am editing is finished. We have published eight volumes.⁹ Of the 500 known spp. & transitives, are old world, 214 are Tropical african.

I doubt if Brazil exhibits anything like [6] the same congestion of spp. as is found in the Malayan region. Hevea elastica, which yield Para rubber, is found for thousands of miles along the coast of the amazon. This could not be paralleled from Malaya.

I quite agree with you as to the paucity of arctic and mountain floras. The reason is that they are mere survivals of wholesale decimation. John Ball¹⁰ pointed out, in the case of the Valais, that the Flora of the [2 words illeg.] is poor compared with that of the southern side of the Alps. The reason is that the one was restocked from a rich area and the other was not.

What you say p. 95 on the arborous character of crimson floras is admirable [7]

I can't make out (p. 97) the [illeg.] of spp. above the mid-temperate zone.

What you say on p. 104 about 'recession to mediocrity' is excellent. So also is p. 123 on causation & mendalism.

I am sceptical about the the superabundance of CO₂ in the Palaeozoic age. (pp. 196, 217). i. It is not clear that plant-protoplasm would stand it; ii. there ought to have been coal earlier than the carbonifeous; iii. there were air breathers at that period.

p. 261 Germinal selection and onwards. This is an entirely novel point of view. I must take time to let it soak in. I will frankly admit that I have always felt it difficult to believe that the horns & the [2 words illeg.] could have had survival values. On the other hand I have always consistently maintained the utility & every [illeg.] of structures. Compare what you say on p. 86[.]

I do not like ‘superfluous vital energy’ p. 273 [8] Is it not making the description the cause? The fact, I take it, is [illeg.] readiness to grow and a superabundance of nutrition. In disease these ^this is exemplified by a tumour. Unchecked exhuberence of growth is certainly exhibited in the most remarkable way by our cultivated vegetables. It is certain they could not be maintained except under artificial conditions. There is some evidence that nature has had to devise direct means to check this exuberance. The function of the pineal gland in man is to control the growth of the legs and prevent 'gigantism'. Your explanation is at any rate better than that of George Henslow¹¹ who said at the Royal Institution that the only possible explanation of a particularly grotesque fish was that the Creator had made it as a joke.

The only time I ever saw Darwin¹²at Kew. I showed him a pitcher of [illeg.] with extremely elaborate appendages and suggested that they could not have utility. He strenously, almost warmly, protested; he said it was [9] impossible to prove that they had not, and if such a view was once admitted, it shut the door to all investigation.

I can only say that this fact in your book is an 'eye-opener' and one of the most courageous contributions to post-Darwinian literature.

On the concluding portion of your book I find myself less open to conviction. It I have never been able to admit a directive principle of Evolution. To do so seems to me to make the Darwinian theory superfluous, and to take a back to Paley¹³ and the Bridgewater treatises. Lord Kelvin¹⁴ seemed to think that inorganic nature was the creation of blind chance, but that organic nature was controlled by Providence. I am content [10] myself to regard the evolution of both as one whole and as the progressive realisation of an 'idea' in the mind of the Creator.

To say that God contemplated & [2 words illeg.] (p. 360) when he provided silica, seems to offer the Sun to scarcely fair criticism for the imperfection of ^{a merely} human device. For a [2 words illeg.], being partly soluble, is a very imperfect appliance. A chemist has just written to me to say that he believes the fact led Darwin into error in his Drosera work, owing to his not being aware of it.

There is hardly a page in your book on which I could not say something. You will probably agree [11] that I have said quite enough. I should not have said anything unless you had invited me to do so.

I can only sum up by repeating my admiration. I have rarely read anything so stimulating

Yours very sincerely | W. T. Thiselton-Dyer¹⁵ [signature]

PS. I enclose a little paper of my own on perhaps the most remarkable of all plant structures. It certainly illustrates 'vital energy'.

W. T. T. D.