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 sh^d. 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 M^r 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

C. Darwin