WCP1440

[1]¹

To W.B Hemsley², Esq.) Firth Hill, Godalming.

August 26th. 1888

Dear Mr Hemsley

You are aware that Patric[k] Geddes³ proposes to exclude natural selection in the organisation origination of thorns & spines, which he imputes to "diminishing vegetativeness" or "ebbing vitality of the species". It has occurred to me that insular floras should a afford a test of the correctness of this view, since in the absence of mammalia the protection of spines would be less needed.

Your study of these floras will no doubt enable you to answer a few questions on this point. Spines & thorns are I believe usually abundant in arid regions and continents — especially in S. Africa where large herbivorous mammals abound. Now if the long-continued presence of these mammals is a factor in the production of spines by nat[ural]. select[ion]. they should be wholly or comparatively absent in regions equally arid where there are no mammals. The Galapagos seem to be such a case — also perhaps some of the Sandwich Islands, and generally the extra-tropical volcanic islands. Also Australia comparatively, and the Madagasca Highlands of Madagasca[r].

Of course the endemic species must be chiefly considered as they h as they have had time to be modified by the conditions. If you can give me the facts, or your general impression from your study of these floras, I shall be much obliged. I see, of course, many other objections to Geddes' theory, but this seems to offer a crucial test.

Believe me | Yours very truly | Alfred R. Wallace. [signature]

P.S. I can find no reference to the point in your "Introduction⁴" — nor in Darwin's⁵ account of the Galapagos⁶ nor in his Origin of Species⁷.

A.R.W.

[1]¹

To W.B Hemsley², Esq.) Firth Hill, Godalming.

August 26th. 1888

Dear Mr Hemsley

You are aware that Patric[k] Geddes³ proposes to exclude natural selection in the organisation origination of thorns & spines, which he imputes to "diminishing vegetativeness" or "ebbing vitality of the species". It has occurred to me that insular floras should a afford a test of the correctness of this view, since in the absence of mammalia the protection of spines would be less needed.

Your study of these floras will no doubt enable you to answer a few questions on this point. Spines & thorns are I believe usually abundant in arid regions and continents — especially in S. Africa where large herbivorous mammals abound. Now if the long-continued presence of these mammals is a factor in the production of spines by nat[ural]. select[ion]. they should be wholly or comparatively absent in regions equally arid where there are no mammals. The Galapagos seem to be such a case — also perhaps some of the Sandwich Islands, and generally the extra-tropical volcanic islands. Also Australia comparatively, and the Madagasca Highlands of Madagasca[r].

Of course the endemic species must be chiefly considered as they h as they have had time to be modified by the conditions. If you can give me the facts, or your general impression from your study of these floras, I shall be much obliged. I see, of course, many other objections to Geddes' theory, but this seems to offer a crucial test.

Believe me | Yours very truly | Alfred R. Wallace. [signature]

P.S. I can find no reference to the point in your "Introduction⁴" — nor in Darwin's⁵ account of the Galapagos⁶ nor in his Origin of Species⁷.

A.R.W.

[1] [p. 43]

To DR. W. B. HEMSLEY

Frith Hill, Godalming. August 26, 1888.

Dear Mr. Hemsley,— You are aware that Patrick Geddes proposes to exclude Natural Selection in the origination of thorns and spines, which he imputes to "diminishing vegetativeness" or "ebbing vitality of the species." It has occurred to me that insular floras should afford a test of the correctness of this view, since in the absence of mammalia the protection of spines would be less needed.

Your study of these floras will no doubt enable you to answer a few questions on this point. Spines and thorns are, I believe, usually abundant in arid regions of continents, especially in South Africa, where large herbivorous mammals abound. Now, if the long-continued presence of these mammals is a factor in the production of spines by Natural Selection, they should be wholly or comparatively absent in regions equally arid where there are no mammals. The Galapagos seem to be such a case — also perhaps some of the Sandwich Islands, and generally the extra-tropical volcanic islands. Also Australia comparatively, and the highlands of Madagascar.

Of course, the endemic species must be chiefly considered, a they have had time to be modified by the conditions. If you can give me the facts, or your general impression from your study of these floras, I shall be much obliged. I see, of course, many other objections to Geddes's theory, but [2] this seems to offer a crucial test.— Believe me yours very truly, | ALFRED R. WALLACE.