To Asa Gray 4 December 1876
Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.
Dec 4. 1876
My dear Gray,
I think I told you that I was going to re-publish my Dimorphic papers, with additions I have become convinced that plants of this class cannot be recognized merely by the varying lengths of pistils & stamens in a few specimens. It is necessary to compare size of pollen grains & state of stigma.1 Therefore I want you much to send me one or two flowers of both forms of Leucosmia & Drymispermum, (mentioned in Amer: Journ of Science Vol 39 p 104—) if not very rare & precious.2 The flowers ought to be rather youngish ones otherwise the pollen will have been shed or lost. My object is to see plants in as many natural families as possible, and if you could spare me flowers of any dimorphic plant, not included in the Primulaceæ, Lineae Oxalidæ, Gentianeæ, Verbenaceæ, Boragineæ, Rubiaceae & Lythraceæ, I should be very much obliged.3
One other question, do any of the dimorphic plants known to you inhabit water or marshes?4 I hope & suppose that you have assistants whom you could direc〈t〉 to look out for the desired specimens.
My dear Gray | Yours ever sincerely | Charles Darwin
Plans to republish his paper on dimorphism with additions [Forms of flowers]. Is convinced it is necessary to compare pollen-grains and the state of the stigma to recognise dimorphic plants. Requests specific plants to test for dimorphism and would welcome examples from any family in which he has not encountered dimorphic species.