Sir Michael Foster on Seed Production and Hybridization (1883) Gardeners' Chronicle

This is part 4. in a six part article on "Hybridization" for other parts click on number part 1; part 2; part 3; part 5; part 6

4, On Some Hybrid Irises. — I find that many have a great objection to the raising of hybrids. From a gardening point of view this is of course wholly unreasonable, seeing how every year sees the birth of hybrids more beautiful and more manageable than their parents ; and even from a botanical point of view the hybridist, it appears to me, deserves praise and not blame. I will say nothing of the evidence, gradually growing stronger, that some of the wild forms of plants regarded by many as species are natural hybrids, and that the distinction between a veritable species and a hybrid is illusory. I simply ask, What is the object of all our investigations into the distinctive characters of plants, into their geographical distribution, and into the proper way of classifying them, except to understand the nature of plants, to find out how they came about, and what is the meaning of all their diverse features? If this be so, then every hybridization must be most valuable, as being a direct experimental thrust into the hidden nature of the two parents. Every feature of a hybrid must have previously existed latent and potential, even if not visible, in one or other of the parents ; and, indeed, every hybridization may be looked upon as a trial to see of what stuff the parents are made. Of course, for this very reason, new hybrids are apt to throw into confusion old classifications, and to upset many a neat clavis : but surely this is a matter over which we should not sorrow but rejoice exceedingly, seeing that we are thereby saved, as it were prematurely, from a serious error. Finding pleasure in my Irises, not only for their beauty, but also for the lessons which they teach, I have not hesitated for some few years past to make numerous attempts at hybridization, and am already beginning to reach results which may perhaps be interesting not only to myself but even to my readers.
Let me first say a word about the natural seeding of Irises. The bare plot of ground which my sarcastic friends call my garden lies on the summit of a chalk hill, not in the soft southern part of England, but in the raw Eastern Counties — a hill, inconspicuous in itself, but appearing something because it rises straight from the flat plains of Cambridgeshire. Here without soil, with a rainfall about the smallest in England, buffeted by winds from every quarter, I make an heroic attempt to grow my plants ; and they are nourished chiefly with my tears. One advantage only I have, that I gather nearly all the sunlight which falls in our dull clime. I mention these things because they have probably something to do with the fact that such plants as do not succumb to my adverse conditions, but reward my pains by living to flower, on the whole seed very freely. I have already found, more than once, that plants which with Mr. Thompson at Ipswich seed with difliculty bear me abundant crops. I am, therefore, amid all my disadvantages, in favourable circumstances for the seeding of Irises.
In the matter of seeding, not only with me but elsewhere, a great contrast may be observed between the beardless (Apogon) and bearded (Pogoniris) forms. With some few exceptions all the former seed freely, I mean without any artificial fertilization ; all the latter, with some few exceptions, seed scantily. At first sight there seems to be a final cause for this. The bearded Irises are in nearly all cases provided with a thick fleshy rhizome, which may be knocked about, cut to pieces, transferred from place to place, dried up, and, in fine, may suffer all manner of indignities without losing its life. Thus the chances of prolonging the individual life are much greater, and hence the necessity of reproducing itself by seed much less than with the beardless Irises, whose fibrous roots are in the majority of cases devoid of a distinct fleshy rhizome, and thus far more liable to destruction. But this view is negated by the facts that the bulbous Irises (Xiphion) — (for a bulb is as good a protection as, or even a better one than a rhizome) — seed quite freely in most cases, and that the Onocyclus group (I. susiana, &c.), which are rhizomatous, and indeed most markedly so, seed quite freely, as far as my small experience goes, if placed under favourable circumstances. Moreover, it seems strange that the bearded Irises should be the ones which do not seed, seeing that in them the arrangements for insect fertilization, such as the complex beard, etc., are much more elaborate, and the flowers are, as a rule, more handsome and conspicuous than is the case with the beardless Irises. And there is no evidence that, either in my region or in the rest of England, insects suitable for fertilizing the bearded Irises are much less common than those suited for fertilizing the beardless ones. I am inclined to think that the actual reason why the beardless Irises seed so freely is because, in some way or other, and for some reason or other, they have learnt the practice of self-fertilization. I say learnt, because the arrangement of anther and stigma is in them, as in all Irises, opposed to self- fertilization, and we are, therefore, led to believe that the Iris in its beginning, was a plant which did not fertilise itself; on the other hand, it is quite open for us to suppose that the power has been preserved rather/than acquired. At all events, I think I have evidence, though not yet sufficiently exact and extensive to be insisted upon, that these beardless Irises can fertilize themselves, even each stigma with its own underlying pollen ; and it is perhaps worthy of remark that in many forms, such as I. spuria, I. longipetala. Sec, the anther is frequently so long as to project beyond and above the stigmatic surface, and thus the pollen from the top part of the anther readily falls on its own stigma.
The bearded Irises, on the other hand, as far as my observations will allow me to judge, are not capable of self-fertilization ; when they go to seed it is because the stigma has received the pollen of another flower. This is all very tedious, I hear some one say ; and yet every one, I venture to think, loving at first a group of plants for their beauty only, will sooner or later find himself entangled and interested in questions of this kind. Besides, such matters are not without practical importance ; for instance, in attempting to hybridise the beardless Irises much more careful precautions have to be taken than is necessary with the bearded forms. It is with certain hybrids of the bearded group that I wish to deal now. As I said above, these, at least the native wild forms, very rarely seed naturally. But there are exceptions. Thus, among the dwarf forms, while the true I. pumila rarely goes to seed, I. chamaeiris, and the allied I. italica, I. olbiensis, etc., seed freely.

With the taller common garden forms seeding is much less common. I. pallida is the one perhaps most prone to seed, and next come some forms of variegata. I. germanica often produces pods, but rarely affords ripe, well-tormed seeds. I have occasionally had a pod from I flavescens, but I have never seen I. florentina so much as even begin to swell its pods. And the results of artificial fertilization either with proper or with foreign pollen follow in much the same order. I have found no great difficulty in getting large, turgid pods, well filled with good seed, from I. pallida and I. variegata; with I. germanica the ovary swells and becomes a pod, but rarely gives sound seed ; and the same with [[SpecFlavescens][I. flavescens]; while every one of the many attempts I have made to fertilise I, florentina have resulted in complete failure.
These facts make me feel inclined to believe that the going to seed or not going to seed is determined much more by the inherent intrinsic capacities of the plants than by the mere fact whether or no pollen has been brought, by insects or otherwise, upon the stigma. That the form of the Iris flower is adapted to insect fertilisation cannot be denied. Indeed, Sprengel states that he was originally led to his views of insect fertilisation by observations on the Spanish Iris (I. xiphium). This is a beardless form ; but the beard seems only an additional contrivance to insect fertilization. On the one hand it is a more conspicuous signal than the coloured blotch on the beardless Iris ; on the other it seems to be of mechanical use, for, as I have actually observed, a bee tries to walk over the beard into the funnel of the flower, and in so doing repeatedly brushes the stigma with its back. Admirably adapted as the flower seems, however, yet the occurrence of fertilisation does not seem to be in any direct relation to insect visits. I have not been able to make as yet any close or careful observations, but as far as I have hitherto seen I. germanica or florentina is as much visited by bees {or other insects) as pallida and variegata, and such of these creatures as are about in the spring seem as fond of visiting I. pumila, which rarely goes to seed, as the other dwarf Irises which seed freely. Nor does the quantity of pollen afforded by the anthers appear to be a very important factor; for several Irises which have abundant pollen do not seed freely, while on the other hand I have repeatedly seen scanty pollen distinctly efficacious.
As is well known, there are many tall bearded Irises cultivated in our gardens which do not occur anywhere in a wild state. Some of them, such as I. aphylla, or I. plicata, I. Swerti, I. neglecta, are of very old standing, and have been admitted by Mr. Baker as species. Besides these there are an immense number of forms, generally spoken of in the nurserymen's catalogues as varieties of I. germanica. I have no doubt at all that I. plicata, oraphylla, and I. Swerti are derivatives from I. pallida ; and moreover, I am inclined to think that they are hybrids and not simply intrinsic varieties.
I. neglecta, for reasons which I will state presently, I believe to be a hybrid. The nurserymen's varieties of I. germanica are derivatives from I. pallida, I. squalens, I. variegata, I. sambucina, I. lurida, and I. flavescens; and my friend Mr. Peter Barr, in his catalogue, makes a very praiseworthy attempt to classify them as varieties of these several species. I believe that all these garden forms also are in ultimate origin hybrids, though the products of the first hybridization probably varied largely afterwards ; and into the large number of forms so far known to me the blood of I. germanica proper, and of I. florentina enters to a very slight degree if at all.
I have spoken of these supposed hybrids as subsequently varying, that is, giving seedling varieties, because in the genus Iris, as so often in other plants, the hybrids, so far from being sterile, appear to seed even more freely than their parents. So much has this now become impressed on my mind, that in the case of any bearded Iris of unknown origin, the fact of its seeding freely would be to me an indication of its being a hybrid. Under the name of I. pumila affinis I received some time ago from my friend Mr. Max Leichtlin a handsome dwarf Iris, which he found in the Botanic Gardens at Vienna, and the origin of which was unknown. He supposed it to be a hybrid, and I am inclined to think that he is right, and that its parents are I. pumila and some such form as I. italica. This plant seeds with even troublesome profusion. Messrs. Haage & Schmidt distribute a somewhat dwarf Iris which they speak of as a hybrid between I. pumila and I. olbiensis. I am inclined to regard this also as a hybrid, though I very much doubt the particular parentage given ; it, too, seeds most profusely. Similarly I. neglecta and many of the tall garden Irises spoken of above seed on the whole more freely than any native tall kinds, except perhaps I. pallida. M. Foster, Shelford, Aug., 1883.

Continued here as part 5;

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