To John Denny 22 July 1872
Down, | Beckenham, Kent.
July 22 1872
My dear Sir
I thank you for yr kind & interesting letter, which has not been too long for me by a single word.1 In my opinion the peltatum case, after you have made some more experiments, wd be worth communicating by itself to the Linn. Soc. But I also strongly think that the other cases wd be well worth giving, with a statement that the parentage of the supposed vars. was not known. You cd state that you cd perceive no marked difference between the 2 sets of vars. which are mutually sterile; & it wd add greatly to the value of yr paper, if you cd get some botanist, whose name is known, to compare the vars & to say whether he cd detect any difference which appeared of specific value.2 Please to remark how strange a fact it is that forms, to all appearance mere vars, shd be mutually sterile, whilst other vars are mutually fertile.
I dare say not one of yr experiments has been vitiated by insects not having been excluded; but you might like to hear that the pollen of a pre-potent form will fertilize a stigma, already thickly coated with its own pollen: I know this experimentally, & in the case of Primula the second dose of pollen was put on after an interval of 24 hours—3 After a grain of pollen has remained on the stigma for about half a day, & all the contents have passed down the pollen-tube, I have found the detection of the shrunken envelope of the grain very difficult.
With my best hopes for the success of yr future observations believe me my dear Sir | yours very faithfully | Ch. Darwin
P.S. I was quite delighted to see the action of the Hort. Socy. about Dr Hooker.—4
Discusses the mutual sterility of some varieties of Pelargonium.
- Letter no.
- Darwin, C. R.
- Denny, John
- Sent from
- Source of text
- Special Collections, Library, University of Otago (DeB MS 55)
- Physical description
Please cite as
Darwin Correspondence Project, “Letter no. 8423,” accessed on 23 February 2017, http://www.darwinproject.ac.uk/DCP-LETT-8423