Cases of "dioecio-dimorphism" as in primroses are widespread. AG always considered them the first step toward bisexuality.
-- 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) 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
- f1 2819.f1Dated by CD's statement in the letter to Asa Gray, 11 August : `I received your note of July 10
th'. See also n. 3, below.
- f2 2819.f2Torrey and Gray 1838--43.
- f3 2819.f3CD did not own a copy of Torrey and Gray 1838--43. The expression `diœciously dimorphous' is discussed in Gray's Manual of botany (Gray 1856, p. 171 n.). In CD's annotated copy of this work (Darwin Library--CUL), this expression is underlined in pencil. CD thanked Gray for these `valuable hints' in the letter to Asa Gray, 11 August .