WCP2759

[1]

28 Mt. Auburn St[reet]., Cambridge, Mass[achusetts].

U. S. A.

Dec[emeber]. 16 1876

Prof[essor]. A. R. Wallace

Parkstone, Dorsetshire, England.

Dear Sir: -

I quite agree with what you say in "Darwinism" on the intergrading of related species. I am inclined to think that more than half the recognized species of American plants intergrade with related species. I also believe that more careful study will show a difference of habitat in such species occurring in the same geographic area, as you suggest.

If species are produced by adaptation to environment or natural selection, it seems to me that two closely related species will never occupy the same habitat and have the same range. But systematic botanists have not yet recognized this distinction in the separation of species.

Moreover all such closely related species occupying different habitats in the ^same geographical area or [2] similar habitats in different, but contiguous areas, will, in all likelihood intergrade at points where they overlap. This seems to me to explain the facts of intergrading, as they appear from a botanical standpoint.

I am not aware that this difference of habitat in related species had yet been proven, or even extensively discussed. In fact, I have found no reference to it except in your "Darwinism", and that after I had already begun to collect material to make a quantitative study of specific variation and intergradation of plants in order to ascertain this very fact. Therefore, I would be glad if you could give me any references bearing on this subject, or suggest the most effective method for studying these intergrading species and their habitats. I have begun by making measurements after the Galton method, but have yet found no accurate method for measuring color.

I would like to ask if it is not possible, even advisable, for the sake of simplicity to unite all such intergrading "species" into one and call them "subspecies" and "varieties" as A. De Candolle¹ and Canes² have done.

Respectfully | J. W. Blankinship [signature[

(Assistant in Botany, Harvard University)