From Asa Gray [10 July 1860]1
– Your observation on Primroses relates to a subject with the general facts
which I am very familiar, though I never thought of the accurate investigation by measurements &c you undertake. I have long ago convinced myself that the two forms are both fertile, but always looked at it as the first step toward bisexuality. When your notion about the probable necessity of cross-fertilization came to my knowledge, these diœcio-dimorphous flowers (See Torr. & Gray, Fl. N. Amer. 2. p. 38)2 occurred to me as a pretty case of arrangement for it. The case is extremely common, in very various families,— tho‘ I did not know it in Primulaceæ. The Rubiaceæ, Borragineæ, Labiatæ, &c &c. are full of it. I think cases can be found of its gliding into structural unisexuality.
Adieu, dear Darwin, | Truly Yours | A. Gray
Cases of "dioecio-dimorphism" as in primroses are widespread. AG always considered them the first step toward bisexuality.
Please cite as
Darwin Correspondence Project, “Letter no. 2819,” accessed on 10 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-2819