To Daniel Oliver 12 [April 1862]1
Down Bromley Kent
My dear Sir
I seldom see anyone, so it is a great pleasure to me to receive a scientific letter & I thank you for your very interesting one.2
First for Primula; I should like to see (pollen of) P. farinosa; but it really is of little importance, so tell your correspondent not to give himself much trouble; I send copy of my paper.—3 I had noticed difference in size of ovules, but slurred the case over, & concluded that I had taken buds of different ages: I have just looked at a couple of large flower-buds of Primrose; in these the ovules were largest in the short-styled, just the reverse of what you say! Have you written “long”-styled for “short”-styled? or is the size a variable point?4 The short-styled certainly produce a greater number of seed; but I did not attend to number of ovules: I will look at a few more of buds of equal age.—
Your discovery about Campanula seems to me extremely interesting; & I am specially surprised at the gradation of the two states on the same(?) plant; I am very glad you will read a paper on this.5 Twice I have had Campanulas & Violets for experiments, & twice I have been prevented observing.6 I can see at least 3 classes of Dimorphism,—Primula & co:—Thymus & co:—Campanula. Violets & co. For the latter cases I have theorised from what I have seen & read on Violets that the final object of the imperfect flowers is to produce seed safely, without any crossing. (so your remarks on the structure please me); the perfect flowers being adapted for getting an occasional cross; but I have not space here to give my reasons for coming to this provisional conclusion.— You will see that according to my notion, the final object of the dimorphism in Violets &c is exactly the reverse of what it is in Primula.—
With respect to Fumaraceæ, I had attended a little to them, when 3 or 4 years ago Asa Gray (& so does Vaucher) advanced this order as one with perpetual self-fertilisation;7 this made me attend more carefully to it, & I am convinced the whole structure of the flower is beautifully adapted to favour an occasional cross.— I have many recorded observations, but God knows whether I shall ever have time to make use of them.8 I write this letter only from memory.
Insects are not indispensable, for all that I have tried set seed without insect aid. It is really pretty to watch a Humble-bee visit Dielytra (& allied forms) Adlumia &c &c & see how neatly its hind-legs rest on the projecting plates on each side of the hood over the stamens & pistil, & push it to one or the other side, & get its body covered with pollen, against which the stigma is rubbed.— This tube has nectary on both sides & the “hood” can be pushed either way & the pistil is straight— Next look at Corydalis tuberosa? & allies (purple flower with white tube & now in bloom) here secreting nectary on only one side, & the hood can be pushed off only on one side, & the pistil is curved (it is straight in Dielytra) towards the gangway into the nectary.—9
Pray look at Corydalis lutea, with nearly similar structure; but with additional curious contrivance; when Bee (as I have often seen) visits flower, it pushes back the hood, & then the pistil moves with a jerk or spring forward.— This movement determines at once the act of fertilisation, though it will take place if the flower is never visited & the pistil never snaps off. (but flowers in this case are less fertile) But I must not run on; & I have written so briefly that you will not understand me.—
With respect to Bees biting holes; this occurs in almost all flowers occasionally, which are difficult to enter; I have never seen it occur in any Fumariacieæ, at least I think not.— But I know of no single instance of this always occuring in any plant— When it does occur, there can be no crossing as you say, & I have some reason to believe that the fertility of flower is diminished; certainly in some cases it would be quite stopped. Oddly this biting of holes occurs chiefly when large masses of the same species are grown together; I shd. like to hear what species of Fumaria you have seen with bitten corolla.—
I am pleased to hear that you are going to discuss Dimorphism in Nat. Hist R. for I have no doubt you will make a very valuable paper.—10 By the way I have been much interested by your Atlantis paper, & rejoice at your conclusion;11 I think, however, you might have made it more popularised, & I will add another criticism, viz that you ought (as I think) to have laid much more stress on migration having taken place during former warmer period.— I wish that your Lectures did not take up so much time, so that you might write on various subjects.12 I do not know whether the diagrams of Catasetum would be worth your taking away from Linn. Soc; but if so they are at your service; & there was a diagram of Primula there.—13 This reminds me that Mr Fitch drew for me cuts of Primula, would you be so very kind as to ask him what I am indebted to him for his kind assistance; though perhaps the Linn. Soc paid for the drawings on the wood.—14
I am nearly certain that Asa Gray (perhaps also in his Manual) told me that the imperfect flowers of some N. American Campanula produced more seed than the perfect.—15 But I keep my notes in such a stupid manner that I cannot refer to single points, only to whole large subjects.
I have written you a frightfully long letter not worth the trouble of decyphering. Another thing just occurs to me which I meant to say whenever we met: viz that if ever you had leisure, you might make a grand essay on the charater of Fr. Water plants, taking, I presume, those whose roots were always covered with water. I presume no one could treat of more than Europe & N. America, though some Tropical country ought to be included.— It would be interesting to see how many had sent one or two colonists into the water: but what would be most curious would be to consider the nature of affinities, & degree of organisation of those groups, in which all the species were aquatic; I strongly suspect they would come out a queer set.— Do think of this.—
Forgive me scribbling at such length, & believe me Yours very sincerely
DO’s observations on polymorphism in Primula and Campanula. CD recognises three classes of dimorphism, as in Primula, Thymus, and Campanula and violets.
DO’s Campanula paper and Royal Institution lecture [Not. Proc. R. Inst. G. B. 3 (1858–62): 431–3].
CD’s interest in Fumariaceae from A. Gray’s comments on "selfing".
Bees bite holes in flowers when same species grows in high density.
Organisation of CD’s notes.
Please cite as
Darwin Correspondence Project, “Letter no. 3504,” accessed on 20 February 2017, http://www.darwinproject.ac.uk/DCP-LETT-3504