Darwin Correspondence Project

Botanic Gardens Edinburgh

July. 23d.

Sir.

I duly received yours of the 2d. I am greatly obliged for your account of the structure of Hottonia. I will be able to had—if I had results—a few experiments on a short-styled form with own-pollen; and also with that from a long-styled form: having been favoured with a few flowers of the latter from a friend. I can also add from observations on dried specimens of the North American H. inflata, as a non- dimorphic species. The style is very short & reaches the anthers: pollen-grains very similar to those of long-styled H. palustris. I should like much to hear whether the H. sessiliflora of Java is dimorphic or not—as it would enable me to include as I believe all the representatives of the genus—but I cannot find a single specimen of it in any of the Herbaria to which I have access. The description of the species unfortunately takes no notice of either stamens or pistil.

I am much astonished with your extracts from Bot. Zeit. respecting the P. longiflora   I have had numerous specimens and never found an approach to the short-styled state: in those cases where styles & stamens differed in length I invariably found the former organ projecting beyond the stamens: anthers always surrounding the mouth of tubes. It is also quite a mistake of Prof. Treviranus to suppose that long-styled P. Auricula is sterile. As bearing on this point however I mention in my paper the long-styled form of P. denticulata, from which I have never been able to get a single seed neither with own-pollen nor that of closely allied species. I had no short-styled form of the species to try it with. Mr. Mc.Nab likewise informs me that though it has now been in cultivation in the Gardens for upwards of 18 years, yet he has never seen it produce a seed.

—It is singular how Koch & Tausch could have hazarded such a statement respecting universal dimorphism in the species of Primula: for I cannot think if they had carefully examined the other forms could have escaped them. Singularly enough we have also made directly opposite observations on P. longiflora! I am glad you gave me an authority to support me as to its being a non-dimorphic species. Though I of course have the fine suite of specimens of this species in the Edinburgh University Herbarium to refer to in support of my statement.

I am gradually getting results of my Primula work. Those from my crosses with differently coloured Primroses are most remarkable. Thus from homomorphic crosses of P. vulgaris & var. alba I got an average of about five seeds per capsule: from the latter fertilised with own-pollen I had an average of eleven. But the most astonishing results were those from a Red Primrose & the common yellow, & white. Reciprocal unions between the former & the two latter have not yielded me a single seed. I also took the precaution to prove that that the plants of the Red & White varieties experimented upon were productive with own-pollen; as I find that many individuals of both varieties will not produce a single seed even after careful fertilisation. The less robust growing plants have alone proved productive with me; more especially in the case of the Red, with the white it is somewhat different. Both varieties have been cultivated in the Gardens here for many years yet Mr. Mc.Nab tells me that he has never known them to produce any seed! In my own mind I certainly have a conviction that I have here an illustration of the attainment of the very zero of fertility between varieties of a species; though I fear my experiments will not be sufficiently numerous to carry a like conviction to the minds of all. Indeed I had some little hesitation in bringing them forward in my paper at all; until I had further opportunities of repeating them. After a careful consideration of those I have already made, I think myself justified in stating them at least. Individuals of varieties perfectly sterile when crossed; yet productive at the same time with own-pollen, is certainly curious if it is not in reality due to the cause I suppose. As you have however so kindly offered to examine my paper; I will leave it entirely in your hands, and you can form an idea from the nature of the evidence on which it is based, whether or not it would be advisable to record it along with my others.

I have been most unfortunate with my unions of Cowslips & Primroses: my experimental plants were accidentally sent down to our Class-room in illustration of the Order; and best of the capsules were taken off. I am very sorry for this as I fear I will be quite unable to give anything like a table of these unions.

My Orchid paper is not published yet: they promised to bring out in the late no. of the Edin. New Phil. Jour. but it was pushed aside for others which they thought were more interesting. It has certainly disappointed me very much. I have spoken to the publisher, however, and he has promised to throw off a few copies of it in a short time; so I hope to be able to send you them sometime previous to the publication of the next Journal. By the way I have made out a few more cases of Individual Sterility in Orchids: I will state them in my next, in case you may need further illustrations.

I know I was wrong in suggesting the slightest modification of results in my last. Pray excuse me. I merely did it under the impression that otherwise, it might afford an argument for some of your numerous carping critics against the view you take, that for example the differentiation the male & female sexual e<le>ments of either form of Primulas have undergone with respect to their homomorphic action was a slowly acquired quality. This I thought was opposed by the non-dimorphic cowslip. At least it appeared to me that any inclined to dispute your views might have instanced it as probably illustrative of the other forms having thus likewise suddenly attained their structural & functional peculiarities. I however, may be quite wrong: anyhow, I will ever remember, & act in accordance with the judicious counsel you have given me.

I regret to find by your last that you was afraid for an attack of scarlet-fever in your family. I sincerely trust this has been awarded, and that all ere this are again enjoying that most invaluable of gifts.

Excuse my hurried scribble. | Very respectfully yours. | J. Scott