To Alphonse de Candolle 4 August 
Down. | Bromley. | Kent. S.E.
My dear Sir
Will you permit me to beg you to interest any young Botanist at Geneva to observe one point for me. But the possibility rests on Lythrum Thymifolia or Hyssipifolia growing near you & being still in flower. Vaucher says (Hist. Phys. Tom. 2. p. 371)1 that these two species are dimorphic like Primula. I have examined several dried specimens of L. hyssipifolia & can see no trace of this fact.2 If either species present any difference in length of pistil & stamens, it is most likely that three forms should be presented. Could you get this point looked at for me; & if possible a few flowers of the two or three forms sent me in a letter.3 I may add that in some species of Lythrum two of the forms have the pistil hidden within the calyx.
I have been trying most laborious experiments on L. salicaria, & am extremely anxious to hear about & see if possible, L. thymifolia.—4
I trust to your kindness to forgive me for troubling you & remain, my dear Sir, with sincere respect | Yours very faithfully | Ch. Darwin
Asks AdeC to observe two species of Lythrum to see whether they are dimorphic as stated by Vaucher. CD can find no trace of this in dried specimens he has examined; "if either species present any difference in length of pistil and stamens, it is most likely that three forms should be presented".
Please cite as
Darwin Correspondence Project, “Letter no. 4263,” accessed on 26 July 2016, http://www.darwinproject.ac.uk/DCP-LETT-4263