To Daniel Oliver   10 March 1877

My dear M^r Oliver

I want to beg your assistance with respect to a subject to which you have attended in your interesting article in the old Nat. Hist. Review; but it will be a mere chance whether you can aid me.¹

First let me thank you for the great trouble which you took, as I hear from my son Francis, in sending me specimens, most of which have proved of the greatest value to me.²

M^r Thwaites sent me from Ceylon many flowers preserved in spirits of Oxalis sensitiva, which proved to be trimorphic; & to my surprize there were on the same flower-stalks cleistogamic flowers, which were long-styled, mid-styled & short-styled, in correspondence with the perfect flowers.³

Now I am anxious to know whether the cleistogamic flowers on other tri-morphic species of Oxalis exhibit the 3 forms, or whether, as I sh^d have anticipated, all resemble one another.

I sh^d have said that I have reason to believe that other trimorphic species of Oxalis do produce cleistogamic flowers— Will you therefore kindly look in the Herbarium at any of the commoner trimorphic species from the C. of Good Hope or S. America, & see if you can discover any cleistogamic flowers. If so, & if you can spare me a specimen, pray mark whether it comes from a long-styled, mid-styled or short-styled plant— You must not waste much time about this; but the point seems to me worth determining.

Believe me with many thanks | yours very sincerely | Charles Darwin