(1921) Unusual Forms Of Iris Flowers

The Gardeners’ Chronicle p.84, August 13, 1921

NOTES ON IRISES.

UNUSUAL FORMS OF IRIS FLOWERS.

Whether monocotyledons have been evolved from dicotyledons, or vice versa, evidence crops up from time to time to show that, ages ago, these two distinct classes of plants were more closely united from a structural point of view than "they appear to be to-day. For many years I have grown some thousands of Irises for market, but it was not until last year that I noticed flowers with abnormal numbers of parts. The illustrations in Fiigs. 34 and 35 represent two types of Iris squalens In Fig. 34 it will be seen that there are five falls and four standards, whilst in Fig. 35 there are four falls and four standards. In each ease there were also four petaloid stigmas, and all the organs were perfect and symmetrically arranged. In one case of Iris germanica there were actually five falls, five standards, and five stigmas, all arranged regularly in true dicotyledonous fashion. Unfortunately, however, before I could find time to make a sketch of this remarkable flower, it had shrivelled up, and I can only record the fact that the parts were arranged as I have stated. I have asked several growers of Irises if they have noticed anything of a similar nature in their collections, and, so far, the replies have in every case been in the negative. Of course, it is only when one grows large numbers of any particular plant that aberrations from the normal are likely to be discovered, and there is no doubt that in market nurseries there are far more cases of abnormality than one would suppose. Owing, however, to the fact that little attention is given to the botanical study of plants that are sent to market as soon as ready, many interesting cases, no doubt, go unrecorded. It may be as well, therefore, to put the Irises here represented on record, so that those interested in teratology may be able to compare them with any other examples that mav arise. I may say that a large number of Iris squalens had the four or five arrangement in the falls and standards as shown in the sketches, and this year some of the plants again exhibited the abnormality. John Weathers, Park Vine, Isleworth.

Replies in Gardeners' Chronicles ;

Unusual Forms of Iris Flowers.

-- I cannot help thinking that Mr. Weathers (see p. 85) will find that the experience of most growers is not the same as his with regard to unusual forms of Iris flowers. At any rate, my experience has been that among the hybrid bearded Irises flowers with two, four, or five parts instead of the normal three are extremely common The well-known Queen of May is a constant offender in producing four-sided flowers, and among seedling Pallidas it is not at all unusual to obtain a plant which is apt to produce flowers in which all the petals drop and appear to be fails. The worst instance that I have known of this multiplication or deformity of the parts was a flower of the plant usually known as Iris sisyrinchium which had no fewer than ten falls. W. R. Dykes- Gardeners’ Chronicles p.140, 1921

NOTES ON IRISES.

UNUSUAL FORMS OF IRIS FLOWERS.

Iris flowers, such as are recorded by Mr. J. Weathers in your issue of August 13, with an abnormal number of segments, both redundant and deficient, have occasionally appeared among my seedlings. Some are evidently accidental, especially the cases of deficient segments ; such flowers, having only two standards and two falls quite regularly disposed, appearing occasionally on weak or late-planted Irises, or as the last flower on a weak branch. Others, with redundant segments, especially if there are more than eight segments, often appear to be cases of incipient doubling, or sometimes due to fasciation. But the most interesting, and by far the most frequent abnormal form occurring among my seedlings is the tetramerous flower having four standards, falls, style branches and stamens— in fact, a perfectly regular flower. This form has never occurred in all the flowers of a plant, but in some varieties there is a greater tendency for these tetramerous flowers to appear than in others.

Among the older standard Irises I have observed it most frequently in Queen of May. The best example among my seedlings is Drake. In this variety, which is a very strong grower, the first flower at the top of all the strongest spikes in a (lump is very often a tetramerous flower. This seems to suggest that the cause of these abnormal flowers with redundant segments is connected with exceptional vigour, and though I cannot give any statistics, as I have not kept complete records of the appearance of these flowers, it is my impression that in the great majority, if not in all these cases of tetramerous flowers this connection of redundamt segments and extra vigour was more or less strongly suggested. It is certainly not the only cause, for many seedlings of the greatest vigour have never had a single abnormal flower, and the fact that the tendency to produce these flowers is hereditarily transmissible shows that the primary cause is more deep seated, and is due to some modification of the germ plasm.

It is on this account that these abnormal yet regular flowers are so interesting, for this "modification of the germ plasm" seems to be of a different nature to the presence or absence of Mendelian factors (or genes of Professor Morgan) which definitely determine a character (in one generation or another). For here is a very large and complex character involving many more and greater rearrangements and adjustments than, for instance, the difference between a membranous and an herbaceous spathe-valve, or between a tall and a dwarf stature. Yet it will appear on one spike and not on an adjacent spike of the same plant. One year there may be several abnormal flowers, and the next year none at all on the same plant. The tendency is there, but something more seems to be needed to bring it out.

For these and other reasons it seems to me (as I first suggested in an article on the Florist's Gladiolus, in Gard. Chron., January 8, 1916, p. 25, and again with respect to Irises, July 7, 1917, p. 1) that these more or less fluctuating departures from the normal form of the trimerous Monocotyledon flowers are of the nature of peloria, and are due to the same or similar causes. I can well conceive that peloria in irregular flowers is evidence of their more or less distant connection with regular flowers, and that therefore, as Mr. J. Weathers suggests, these abnormal flowers of Irises, and other Monocotyledons may be evidence of their remote connection with Dicotyledons.

I do not know if any special cytological study or any general investigation into the causes of peloria has been made. Such study and investigation would be full of interest, and might well throw unexpected light on some problems of heredity. If these abnormal flowers are indeed of the nature of peloria, it would be useful to horticulturists (since it would give suggestions how to make use of them) to know whether peloria is a retrogressive (atavistic), or a progressive phenomenon — or perhaps either. Does it represent the cropping up of something acquired by ancestors, so remote that it has sunk down into the general constitution of the germ plasm, and is no longer controlled by Mendelian factors, or does it represent an incipient new character controllable eventually by a Mendelian factor which is not yet fully developed? Or is it merely the result of an imperfection of working in some step of the ontogenetic process. A. J. Bliss-- Gardeners' Chronicles p.149, 1921

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-- BobPries - 2014-06-19