(1914) The Reticulata Group by Dykes
Gardeners' Chronicle p.143, February 28, 1914
NOTES ON IRISES.
THE RETICULATA GROUP.
The first sight of the confused fragments of a puzzle which have to be fitted together is apt to be disheartening. Scarcely any two pieces seem to belong together, and the majority, indeed, appear to be so detached from the rest as to be quite meaningless. Such has hitherto been my feeling with regard to the disconnected facts that have constituted our knowledge of the group of early-flowering bulbous Irises, of which I. reticulata (see fig. 64) is the best-known example. It cannot be pretended that all the fragments can yet be made to fit together into a complete picture, but it is, perhaps, possible to suggest some definite arrangement and to ask whether facts within the knowledge of others who are interested in the group seem to them to fall into their places in the scheme.
The chief difficulty lies, of course, in obtaining specimens of wild plants from known localities. Importers and collectors are only too inclined, perhaps not unnaturally, to be reticent as to the precise localities from which their supplies come, and herbarium material is not always sufficiently carefully prepared to enable us to see clearly the somewhat minute points of difference.
Anyone who has grown I. reticulata, I. histrio and I. histrioides must have noticed that there are marked differences in the methods of increase of these plants. Flowering bulbs of the two latter species form round their bases a cluster of as many as twenty or thirty small bulblets, no bigger than, and not unlike in outline to, grains of wheat. I. reticulata, on the other hand, forms a much smaller number of relatively large bulbs differing considerably in size one from another. The smallest, however, is usually three or four times the size of the bulblets formed by the other two species. As far as my information goes, I. reticulata is confined to the Caucasus Region, and it is only there that Irises are found which increase in the same way. All the other members of the group form the innumerable bulblets already mentioned, and come from further south. The only exception is I. Bakeriana, which is easily distinguished by the character of its foliage, as we shall see later.
There can, I think, be little doubt that the deep violet-blue I. reticulata of our gardens is not the commonest form of that species in its native home. Indeed, I have so far failed to find any scrap of evidence to prove that it is not merely a colour form of garden origin. Bieberstein's original figure (Cent. Plant. Bar. Taur. Cauc. I. t. 11, 1810) does not even justify the assumption that this is his type. On the contrary, his drawing represents much more faithfully the red-purple flowers, which have always been the product of any bulbs which I have received direct from the Caucasus, and also of those plants that I have raised from seeds from the same source. The actual shade of red-purple is apt to vary and the blade of the falls is usually more or less conspicuously veined ; the style-branches are broader than the haft of the falls, and the standards, also, are broad and tend to curve inwards to meet each other instead of pointing outwards at nearly the same angle as the style-branches as do those of I. reticulata.
The view that a red-purple flower is the common wild form is supported by the fact that self-fertilised seed of the type has never given me anything but red-purple forms. This has also apparently been the experience of others, and yet it is a result which no Mendelian theory seems able to explain.
There is yet another tone of colour, which is found among the forms of this Caucasian Iris. It is a peculiar slaty blue, sometimes quite dark, and sometimes so pale that one sturdy example has even received the name of Cantab.
As we leave the Caucasus region and go further south, we come to the home of I. histrioides in the neighbourhood of Amasia or Amas. Its habit suggests that it is an inhabitant of mountainous districts where the winters are severe, for the flowers come up almost simultaneously with, and sometimes even before the leaves. The flowers are flatter and less funnel-shaped than those of the Caucasus group, and of a vivid blue colour, except in the upper part of the blade of the falls, where there occurs a triangular white patch veined and dotted with blue. All these characteristics are found in home-raised seedlings of this species, and, as has been already observed, it differs sharply from the Caucasus plants by its method of increase.
With I. histrioides I am inclined to connect somewhat closely the plant to which Michael Foster gave the name of sophenensis, in memory of the fact that it came to him from the neighbourhood of Kharput, a district which in ancient times bore the name of Sophene. This Iris has flowers of the same shape as those of I. histrioides, but smaller. In neither does the central ridge on the falls fade away, as in I. reticulata ; in both it is carried all along the haft, as was also the case in Leichtlin's purpurea. The latter does not now seem to be in cultivation, but this feature and its short leaves are perhaps enough to justify us in assigning it to this group of plants. We seem also to have lost the colour-forms of sophenensis, which Foster tells us (Bulbous Irises, p. 7) may vary from red-purple to a lightish blue. The only form which I know, and which comes true from seed, is of a pale blue colour, with a lemon-yellow central ridge, much resembling a rather small pale histrioides. Among seedlings of the latter, variation in the exact shade of colour occurs both in the flowers as a whole and in the yellow ridge on the falls.
Going still further south, we come to the region where I. histrio (see fig. 65) is native. Our difficulty here lies in the fact that it is no longer possible to say with certainty to which of two distinct plants the name was originally given. It is, perhaps, rather more probable that it was bestowed on a plant with upright standards and very conspicuously blotched falls, which seems to be confined to Palestine, if not indeed to Lebanon.
This Iris has been distinguished as histrio orthopetala, and it is evidently closely allied to the form with divergent standards and lees conspicuously blotched falls, which is common in the neighbourhood of Marash, and which is now commonly supplied by the trade for the more showy orthopetala. Both produce numbers of minute bulblets, but they differ from the two groups we have already considered by the fact that their foliage, though longer, is more slender and less erect. It is far less rigid, and seems always to begin to curve as soon as it emerges from the soil. The prevailing colour of the flowers is a blue-purple, and the falls are either dotted or veined more or less distinctly.
It is interesting to notice that of this Iris, too, there is now known a red-purple form, atropurpurea. As reticulata, and Krelagii only differ in colour, so does this plant resemble what is probably the northern form of histrio in every respect but that of colour, except that the central ridge is here non-existent, though the black tubercles that dot the low ridge in histrio are here conspicuous as raised points along the central line of the haft of the falls.
Further south still, we come to I. Vartani, which is hardly more than another development of I. histrio. It is distinguished by the length of ite style-crests, and for us in the north by its inability to survive our climate for more than a year or two at the most. Of the white form of I. Vartani, some examples are beautifully spotted with blue, and we can only regret that this Iris has such a poor constitution.
There remain two outlying species, which are easily separated. To the west, in Asia Minor, occurs I. Danfordiae (see fig. 66), which is distinguished by its minute bristle-like standards and by its yellow colour ; while to the East is found I. Bakeriana, whose eight-ribbed leaves divide it at once from all the other Irises we have considered. That I. Danfordiae has been described under more than one name is due not to the variation of the olive-green markings which sometimes occur on the blade of the falls and on the backs of the style-branches, but to the fact that the first-described herbarium specimens had lost their outer bulb-coats, with the result that the description did not mention their reticulated structure. Baker was thus led to class this Iris among the Junos on account of its minute standards, and it was only when the plant was rediscovered by Bornmuller that Haussknecht, seeing the reticulated bulb-coats, thought he was describing a new species under the name of I. Bornmulleri.
Definite dates for the flowering of these plants are most misleading. This year I. reticulata is in full flower in the middle of February, while I have known it so late as the last days of March. And yet, if, as seems not improbable, all our stock of I. reticulata has arisen by division from a single bulb, we might reasonably expect it to be much more constant in its time of flowering than any other of these species, where seedlings are innumerable and differ considerably in their time of flowering. For instance, this season I had some I. Krelagii in flower in the last days of November, though this is no doubt exceptional, while others have yet to open their buds at the end of February. Much depends, I believe, on the date at which the growth of the previous year was ripened off, and on the weather during the late autumn and early winter. The embryo flower is already in the bulb when we plant it in the autumn, and it is not difficult to imagine that external conditions have great influence on the flowering-time of bulbs which develop their flowers with such amazing rapidity as do these small Irises. My experience is that imported bulbs and those that have been lifted flower earlier than those left in the ground, and this is probably to be explained by the fact that the ripening has been more complete.
There is one other point that may be of some interest. I. Bakeriana is admittedly of poor constitution, and apparently nowhere in England does it do really well. For several years now I have grown it side by side with a beautiful hybrid form, of which the late Max Leichtlin sent me a single bulb under the name of Bakeriana melaina. The latter increases regularly by offsets, and this year there have appeared ten flowers, though the type has been flowerless. Melaina has six-ribbed leaves,, and is probably a hybrid of Bakeriana and some reticulata Iris. Its falls are of the richest velvety-violet, and the interest of the plant is that there are now considerable differences among the flowers produced by the different bulbs in the extent of the triangular white patch at the throat and of- the arrangement and number of the dark-violet blotches upon it. Seeing that such differences, small though they are, do undoubtedly arise among the individuals obtained by vegetative increase, we can form some idea of the possibilities of variation among the forms of these Irises which nature has evolved by sexual reproduction.
W. R. Dykes, Chartcrhouse, Godalming.
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