From John Scott 3 March 1863
Botanic Gardens Edinburgh
March. 3d. 1863.
I am glad to hear that the variation of Imatophyllum, will be of service to you.1 I was afraid that it might be of too short a standing for your noticing. It is certainly a very striking one, and may perhaps be the origin of a remarkably distinct race. I will be glad to afford every particular regarding it, you desire.
I have been endeavouring to get seeds of the wild Maize, which occurs on the Rocky Mountains; from description it appears to be remarkably distinct from any cultivated form.2 Crosses with the latter might afford most interesting results: Do you regard it as the parent of the numerous forms now in cultivation? I suppose it has only as yet been found wild in the New World. I am daily expecting a selection of the most dissimilar varieties grown by Barr & Sugden.3 So with those you have favoured me with, I will have a variety of subjects to work upon. I am very desirous, however, for the wild form, but I know not where to get it. I have searched the University Herbarium here, but it does not contain a single fertile specimen.
Are the Passifloras mentioned by you in Origin, invariably sterile when treat with ‘own-pollen’; or is it a local occurrence?4 P. quadrangularis, for example, fruits freely in some hot-houses, in others, though flowering most profusely it obstinately refuses to fruit. In our gardens a form perhaps a variety of the former called Bonapartea will not set a single fruit. It may, however, be otherwise in another locality: Will you be so kind as favour me with the names of any perfectly sterile species, with “own-pollen”.? as I find that some of the species I had thought to be sterile are only locally so,: If such could be rendered fertile by application of pollen from other species, would they be of any service to you? I would much like a little information on these points; as I am working somewhat blindly: I have had yet little experience. I have the same difficulties with Lobelia:5 I have made your desire known to Mr. Mc.Nab.6 He informs me that he has already communicated all the information he could gather on weeping-trees; & inheritance of character from seeds, to M. Neuman of the Jardin des Plantes; who he supposes will shortly publish on the subject.7 I do not think, however, from what I have heard him saying, that he has had much practical experience in these matters; his remarks, will I believe principally be founded on the experience of others. What the results may be I know not I am rather inclined to think they will be of a negative nature So far as I can ascertain—from the large experience of some of the nursery foremen here—the character rarely if ever—appears amongst the seedlings.
I did not mean to say that bisexual plants are more variable than unisexual, all that I intended, was, that the former presented a greater number of naturally established varieties, than the latter.8 This I believe, to be a consequence of the more intimate relation of the sexual organs: as affording a better chance for these being imbued with similar formative tendencies, than occur in the unisexual arrangement. This opinion I hold partly on the grounds that similar variations will rarely appear in a number of individuals at any given time— much more frequently variations will be peculiar to individuals, or even portions of such will be originally representative: and thus in unisexual plants, the embryo must necessarily in general be the resultant of organs imbued with dissimilar formative tendencies—the normal specific, & a diverging form. This combination then causing as it does an immediate change in the conditions originating the latter forms and acting upon the most susceptible stages of the organism; will as I believe, cause an immediate reversion in the embryonic resultant, to the normal specifical form. This I think is fully supported by the results of crossing hybrids—incipient forms—with one or other of their original parents, established forms—as we see by a few successive crosses the other form entirely eliminated. Considering then the results from crossing of hybrids—which be it remembered are products of well established forms—what may we expect from such in the case of accidental variations versus the normal forms. Again, considering the truly casual agencies employed by Nature for effecting fertilisation in the vegetable kingdom; I really, candidly speaking, find great difficulty in understanding how species can possibly be manufactured by an innate, continuously watchful, selective principle. There seems to me a necessity for admitting the occasional actions of a superinduced power to explain the establishment of new forms of vegetative life. The struggle for existence, does not I think fully meet the difficulty—more especially as applied to annuals—inasmuch as the strongest individuals may be continually fertilised by the weaker, and thus constantly check the domination of their progeny.9 Again supposing individual utility alone, as the great end striven after by Nature in the metamorphosis of organic beings; why should there necessarily be a dependence between the internal structure & external form?
The great morphological differences of the sexual forms of Catasetum, for example, seem to me—though I may be quite wrong—scarcely consistent with a mere regard to specific utility.10 Is it not highly probable that in their native wilds, different insects will visit the different forms: and thus somewhat frustrate the plans of Nature. Does the occasional occurrence of the three sexual forms of Catasetum on one spike, not oppose the view that these forms were attained by a gradual modification? On the latter view, ought we not to have expected intermediate forms only? The metamorphosis you mention in Orchid Book on the authority of Mr. Rodgers is most remarkable;11 more especially if we are right in regarding the hermaphrodite Myanthus as the original progenitor? Such an occurrence seemingly disproves what I hinted at in my last regarding Acropera, still no variation having ever been observed in the latter indicates a morphological status which may justify us in anticipating a homomorphic progeny.12
I have thus hurriedly and imperfectly attempted to lay before you a few of the difficulties, which have presented themselves to me, while considering species as products of Natural Selection; these & kindred points I have taken up in my paper.13 But I know not whether I will yet have made my view sufficiently clear; I fail so completely in expressing myself: as I would like. I hope you will excuse me for troubling you with this subject as after all I may be quite wrong—though it has engaged me now for sometime.
In respect to the opinion that homomorphically fertilised Primulas, will produce their own-form only—I may remark that it occurred to me when I first considered the bearings of these plants upon my views. Since: I have examined the different forms very carefully, and I find in concordance with your observations—that the two forms are most decidedly permanent.14 I have seen what, I suppose may be a similar case to that referred to by you on the authority of Mr. Wooler: viz, a long-styled variety of P. vulgaris, producing in early spring a number of short-styled flowers.15 But—mark—there was no change in the position of the stamens: these as far as my observations go are always permanent. From this permanency then I at once concluded as above; having a firm conviction that established seed-variations, will always produce their own characters only, when kept pure: this I anticipate as the result of Vegetable Parthenogenesis—when satisfactorily established.16 Some of the Cryptogams may be already mentioned as producing female forms only by parthenogenesis, e.g. certain Mosses & Chara. I thus regard Primula & Acropera as parallel cases: I would expect different results from Catasetum &c where individuals still produce the different forms. I do not believe that the relative lengths of stamens & pistils in the two forms of Primula could have been attained if these had been fertilised by other than own-form pollen. I am inclined to suppose that they even yet under cultivation, might be caused to revert by continuous crossing of the two forms. P. Sinensis is a case in point—which you first drew my attention to—being regularly raised from seed: and here we find pretty frequently a form with stamens & pistils equal.17 These points, I likewise consider in my paper.18 I may mention that I have raised long-styled plants of P. cortusoides only from own-form pollen. As I had little seed however, I raised only a few plants, consequently I could lay no particular stress on the experiment.
However, I thought I had evidence of such from varieties of P. vulgaris in the gardens here: there being beds of these plants—all of which are long-styled. I thought, therefore that they must have been propagated by seed. I have now asked Mr. Mc.Nab their history and he informs me that have been merely propagated by division. I have, however, a few seedlings of different forms of Primula all homomorphically fertilised—I expect some of these will be in flower shortly, and afford us some more information on this point.19
I am trying at present homomorphic crosses, with different coloured flowers of Primula vulgaris &c.20 I am following out your hints likewise on decreased fertility between varieties presenting only variation in colour, it may perhaps be a more common occurrence than is supposed.21 I will be much obliged if you favour me with a perusal of Asa Gray’s 2d. review of Orchid Book.22 I will return it immediately. I am busy at present with a Bletia;23 I have at last been perfectly successful in my attempts to fertilise Gongora—it is by forced & unnatural work however—I have no less than fourteen capsules on a single spike swelling beautifully—I could almost have wished that it had been otherwise.24 I will give you particulars when I write again, as I fear I will have already exhausted your time and patience.25
I remain | Sir | Yours very respectfully | J. Scott
JS criticises natural selection as based on an innate "continuously watchful selective principle".
Seeks seed of wild Rocky Mountain maize.
What is CD’s view on origin of maize?
Seeks information on self-sterility of Passiflora and Lobelia.
Weeping habit of trees.
Intended to say bisexual plants presented more established varieties than unisexual, not that they are more variable.
Explains his opinion that homomorphically fertilised Primula will produce only their own form. Is trying homomorphic crosses with different coloured Primula varieties.
Asks to read Asa Gray’s 2d review of Orchids.
Has finally successfully fertilised Gongora, but it was done by unnatural means.
Please cite as
Darwin Correspondence Project, “Letter no. 4021,” accessed on 5 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-4021