Synopsis of the known Species of Iris by John Gilbert Baker

Gardeners' Chronicle p526, April 22, 1876

Transcript:

A SYNOPSIS OF THE KNOWN

SPECIES OF IRIS.— I.
The genus Iris has always been a great favorite with cultivators. Many of the species are extremely beautiful, and nowhere amongst the hardy petaloid monocotyledons can we obtain such variety in colouring and habit and such a continuous show of bright-coloured flowers with so little expenditure of money and trouble. As a synopsis suitable for the use of cultivators is greatly needed at the present time, I propose in this paper to classify the known species under their groups, to describe them in English, and to give references to the figures which are scattered so copiously through the Botanical Magazine and other gardening periodicals. Nearly all the known species have been figured, though unfortunately here, as in the case of the Lilies, the octavo size of the periodicals is not large enough to do them full justice, but it is to be hoped, that now that the taste for them has revived, that some one will undertake to do for Iris what Mr. Burbidge has done for Narcissus, and what Mr. Elvves is doing for the Lilies.

Literature of the Genns. — Although Iridaceae as a natural order have been, considering their beauty, botanical interest and popularity with cultivators, wonderfully neglected by botanical monographers, the literature of the genus Iris is very extensive. Leaving out of count the pre-Linnaean writers (and an account of what was done in the genus before the time of Linnaeus would form by itself the material for a very interesting article), and leaving out also Floras that relate to special countries, the following are the principal general works which the student of Irises requires to consult. In the first edition of the Species Plantarum of Linnaeus, published in 1753, eighteen species are characterized. In the second edition, bearing date eleven years later, there are twenty-two published two species In Thunberg's Disserlatio, published in 1782, about twenty extra-European species are added, and the number is raised to forty-five, but Thunberg, in his circumscription of the genus, includes not only what we call Iris now, but also Moraea, Vieusseuxia, and the American Lansbergia. Still using the term in the same wide acceptation as Thunberg, Willdenow gives fifty-four species of Iris in the first volume of Species Plantarum in 1797, Persoon sixty-five species in the first volume of his Synopsis Plantarum in 1805, and Roemer and Schultes ninety-two species in the first volume of their Systema Vegelabilium in 1817. There are also excellent monographs by Lamarck in the third volume of the Encyclopeie in 1789, and by Vahl in the second volume of his Enumerato in 1806. Gawler in the first volume of the Annals of Botany of Konig and Sims took out of Iris the mass of Cape species placed there by Thunberg and placed them under Moraea, a genus first named by Miller, which was kept up by Linnaeus, but in which Thunberg had placed a different set of plants. Gawler (who afterwards took the name of Ker) was the principal authority in England on the genus for the first quarter of the present century, and although he never wrote a complete monograph of Iris, he figured and described a great many of the species in the Botanical Magazine gave an enumeration of all the known species under tab. 986, and still later a full list, with full synonymy, both pre-Linnean and post-Linnean, which occupies twenty-five pages of his Gemra Iridacearum published at Brussels in 1827. Of modern monographs of the genus there are two, the first by Spach, which is printed in three different places — in the fifth volume (beginning at p. 89) of the third series of the Annales des Sciences Naturelles, in the first volume (p. 816) of Walper's Annales and in the thirteenth volume of Spach's Vegitaux Phanerogames (p. 12); and the second by Dr. Klatt, of Hamburg, in the thirty-fourth volume of the Linnaea and revised as regards classification in the Botanische Zeituing for 1872. I wrote a paper on the group with a bulbous root-stock (Xiphion) in the ninth volume oi Seemami's journal 1871, p. 10.
As the genus stretches in the Old World from Britain and Scandinavia to the Canaries, Abyssinia, the Himalayas, Japan, and South China, and in the New World from the arctic circle to California and the Southern United States, it enters more or less into all the innumerable local floras of the Northern hemisphere. Of these the book that contains an account of the largest number of species is Ledebour's Flora Rossica.

Circumscription of the Genus, — As I have just said, Thunberg and the monographers that wrote in the early part of the century gave the genus Iris a far wider extension than we do at the present time. It is very difficult to settle where the bounds of the genus should be placed. There is, in point of fact, no well-defined line of limit between the plants that Thunberg included, if we leave out the American Lansbergia (Iris martinicensis, Linn.). All of them have distinctly dissimilar outer and inner perianth-segments, and petaloid stigmas with a deep bifid crest, opposite to and overwrapping so as to hide the anthers. The following are the principal subdivisions into which Iris, in a Thunbergian sense, has been separated, with their leading characters and geographical range : — • I. Iris. — Root-stock a rhizome. Tube above the ovary absent or present. Inner segments of the perianth erect, outer reflexed. Filaments always quite free. Confined to the northern hemisphere.

II Xiphion. — Root-stook a tunicated bulb. Tube above the ovary absent or present. Outer segments of the perianth just as Iris, the inner either erect, or, in the section Juno, spreading horizontally. Filaments free, or in section Gynandriris, loosely connate with the style. Mediterranean region, Orient and Abyssinia.

III. Dietes. — Root-stock a rhizome. Tube above the ovary none. Inner segments of the 'perianth less different from the outer ones than in Iris, and spreading with them falcately. Stamens free. Cape, one species United States, and one Australian.

IV. Morica. — Root-stock a tunicated cormor bulb. Tube above the ovary none. Flowers more fugitive than in Iris, the inner segments generally spreading falcately with the outer ones. Filaments usually-joined in the lower part, sometimes entirely free. Many species. All plants of the Cape.

V. Ilelixyra. — Exactly Morrea, except that there is a long tube between the ovary and perianth-segments. One species. Cape.

VI. Vieusscuxia.^Wi^ Peacock Irises of the Cape. Root-stock a tunicated bulb ; tube above the ovary none ; inner segments of perianth minute, erect, usually with a distinct claw and three distinct cusps ; flowers fugitive ; filaments united up to the very top. Six or eight species, all Cape.

If Iris be divided at all I think these are the most satisfactory subordinate genera. Both in Liliaceae and Iridacea; it is a great help to the memory to be able to marshal the genera into a bulbous and non-bulbous series, and if we use this subdivision, Iris and Dietes go into the second, and Xiphion, Morcer, Helixyra, and Vieusseuxia represent them amongst the bulbs ; but, as I have already indicated, there is really no clearly defined line of limit in floral structure between the six. But many recent authors go still further in the way of subdivision. Iris, as above characterised, answers to four of the genera of Dr. Klatt's monograph — Oncocyclus,[Neubeckia, Hermodactylus, and Iris; and Xiphion to three — Xiphion, Coresanthe, and Gynandriris. In this present paper I intend to use Iris and Xiphion in the sense indicated above, and to confine my synopsis to these two, of which the species now known are not far short of a hundred.
Sub-genera of Xiphion and Iris. — The following are the groups or sub-genera, very unequal in size, under which I intend to arrange the species :^

Genus Xiphion of Tournefort and Miller.
Section 1. Euxiphion. — Inner segments of the perianth erect, nearly as long as the outer ; filaments free.
Examples — X. vulgare, X. latifolium, X. reticulatum.
Section 2. Gynandriris.^lxwizx segments of the perianth erect, nearly as long as the outer ; filaments loosely joined to one another and the style. Example — X. Sisyrinchium.
Section 3. p/^;?!?. — Inner segments of perianth minute, spreading horizontally between the claws of the outer ones. Examples— X. persicum, X. caucasicum.

Genus Iris of Tournefort and Linnaeus.
Section 1. Hermodactylus.—Outer segments of the perianth, or, as Miller calls them, '* falls," neither bearded nor crested ; root-stock a digitate tuber. Example— I. tuberosa.
Section 2. Apogon. — Falls neither bearded nor crested. Examples— I. Pseud-Acorus, I. laevigata, I. sibirica.
Section 3. Oncocyclus.^YaX\?> hairy on the surface but not regularly bearded. Examples — I. susiana, I. iberica.
Section 4. /'i7«'t7/;/r/j, — Falls bearded down the claw. Examples — I, pumila, I. florentina, I. germanica.
Section 5. Evansia.—YaS\^ crested down the claw. Examples — I. cristata, I.japonica, I. tectorum.
Section 6. Hexapogon.^QM\.fix and inner segments of the perianth both bearded down the claw. Examples — I, filifolia, I. falcifolia.

In distinguishing the groups and species the following are the principal points to which attention should be directed : — Root-stock, — The difference between a rhizome and tunicated bulb furnishes the most tangible difference between Xiphion and Iris, as here understood. In Xiphion, as in Crocus, the nature of the tunics, whether membranous or fibrous, furnishes a good mark of distinction. Compare, for instance, in this respect X. reticulatum with X. vulgare. In Iris only I. tuberosa stands out from the rest by its digitate tuberous root-stock.
Z^jcW. —There are three principal types of leaf —the narrow tetragonal type, shown in Iris tuberosa and Xiphion reticulatum ; the linear type, shown in Iris sibirica and prismatica ; and the sword-shaped or ensiform type, as shown in Iris Pseud-Acorus and germanica.
Stems. — A small set of species have no leaves to the stem, but the great mass are furnished with leaves on the stem, like those of the basal rosette reduced below the spathe- valves. Iris pumila and a few others never produce more than a single flower from a stem, but the great majority of the species have a forked corymbose inflorescence and two or many flowers.
Spathe-valves.—'X\v^ spathe-valves are always at least two-valved, and greatly altered in shape and texture from the original foliar type. Their shape and texture furnish often good specific characters

Flmver.—XX. is in the perianth that the main distinctive characters of the different kinds are to be found. In the structure of the ovary all the kinds are substantially alike. The absence or presence of a tube above the ovary, and its length, and the proportion it bears to the segments, is a point to be carefully noticed. The segments are always six in number, in two rows of three each. The outer three are always reflexed when the flower expands, in shape obovate, with a distinct claw, and nearly always larger than the three inner ones. The best differential character in the genera is furnished by the way in which these three outer segments are decorated down the claw and the keel of the lower part of the face. Sometimes, as in Iris tectorum and cristata, they have a distinct petaloid crest ; sometimes, as in Iris germanica and florentina, a keel of dense hairs, which is called in the descriptions a beard ; sometimes, as in Iris Pseud-Acorus and spuria, neither crest nor beard.
Miller calls the three outer reflexing segments of the perianth "falls," and the three inner ones, which, in all the plants with which we are concerned, except the section Juno of Xiphion, stand straight up in the fully-expanded flower, "standards;" and, although these terms have been little used by later writers, they are so convenient and expressive that I should like to revive them again, and intend to use them in my descriptions. Mr. Barr at my sugge-ilion has used them in this sense for the last two or three years in his catalogues.

Stigmas and Stamens. — It is not necessary for me to take up space here by describing the peculiar structure of the stigma, but I often find that gardeners who have a fair knowledge of botany do not understand the organography of an Iris flower— which parts are floral wrappers and which reproductive organs. I need scarcely say that any one who wants to understand these plants ought to begin at the very outset by getting clear ideas upon this head. The very special form of the stigma is uniform through both Xiphiun and Iris, though there is considerable modification in the size and shape of its two crests.

Ovary and Fruit. — The capsules often furnish good specific marks by size and shape, and this set of characters has been greatly overlooked. A set of drawings of Iiis capsules [and seeds] made from fresh specimens would be a useful contribution to our knowledge of the genus. J. G. Baker, in 1753, eighteen species are characterised. In the second edition, bearing date eleven years later, there are twenty-two. In Thunberg's Disserlatio, published in 1782, about twenty extra-European species are added, and the number is raised to forly-five, but Thunberg, in his circumscription of the genus, includes not only what we call Iris now, but also Morrea, Vieusseuxia, and the American Lansbergia. Still using the term in the same wide acceptation as Thunberg, WiUdenow gives fifty-four species of Iris in the first volume of Species Plantarum in 1797, Persoon sixty-five species in the first volume of his Synopsis Plantarum in 1805, and Roemer and Schultes ninety-two species in the first volume of their Systema Vegelabilium in 1817. There are also excellent monographs by Lamarck in the third volume of the Kncydope He in 1789, and by Vahl in the second volume of his Eniimeratso in 1806. Gawler in the first volume of the Annals of Botany of Konig and Sims took out of Iris the mass of Cape species placed there by Thunberg and placed them under Mora;^, a genus first named by Miller, which was kept up by Linnceus, but in which Thunberg had placed a different set of plants. Gawler (who afterwards took the name of Ker) was the principal authority in England on the genus for the first quarter of the present century, and although he never wrote a complete monograph of Iris, he figured and described a great many of the species in the Botanical MagazinCj gave an enumeration of all the known species under tab. 986, and still later a full list, with full synonymy, both pre-Linnean and post-Linnean, which occupies twentyfive pages of his Gemra Iridacearum^ published at Brussels in 1827. Of modern monographs of the genus there are two, the first by Spach, which is printed in three different places — in the fifth volume (beginning at p. 89) of the third series of the Annales des Sciences Naturelles, in the first volume (p. Si 6) of Walper's Annales^ and in the thirteenth volume of Spach's Végétaux Phanerogames (p. 12); and the second by Dr. Klatt, of Hamburg, in the thirty-fourth volume of the Linmra^ and revised as regards classification in the Botanische Zeitiin^ for 1872. I wrote a paper on the group with a bulbous root-stock (Xiphion) in the ninth volume oi Seemami's foitrnal^ 1871, p. 10.

As the genus stretches in the Old World from Britain and Scandinavia to the Canaries, Abyssinia, the Himalayas, Japan, and South China, and in the New World from the arctic circle to California and the Southern United States, it enters more or less into all the innumerable local floras of the Northern hemisphere. Of these the book that contains an account of the largest number of species is Ledebour's Flora Rossica.

Circumscription of the Genus, — As I have just said, Thunberg and the monographers that wrote in the early pare of the century gave the genus Iris a far wider extension than we do at the present time. It is very difficult to settle where the bounds of the genus should be placed. There is, in point of fact, no well-defined line of limit between the plants that Thunberg included, if we leave out the American Lansbergia (Iris martinicensis, Linn.). All of them have distinctly dissimilar outer and inner perianth- segments, and petaloid stigmas with a deep bifid crest, opposite to and overwrapping so as to hide the anthers. The following are the principal subdivisions into which Iris, in a Thunbergian sense, has been separated, with their leading characters and geographical range : — •

I. Iris. — Root-stock a rhizome. Tube above the ovary absent or present. Inner segments of the perianth erect, outer reflexed. Filaments always quite free. Confined to the northern hemisphere.

IL Xiphion. — Root-stook a tunicated bulb. Tube above the ovary absent or present. Outer segments of the perianth just as Iris, the inner either erect, or, in the section Juno, spreading horizontally. Filaments free, or in section Gynandriris, loosely connate with the style. Mediterranean region, Orient and Abyssinia.

III. Dietes. — Root-stock a rhizome. Tube above the ovary none. Inner segments of the 'perianth less different from the outer ones than in Iris, and spreading with them falcately. Stamens free. Cape, one species United States, and one Australian.

IV. Morica. — Root-stock a tunicated cormor bulb. Tube above the ovary none. Flowers more fugitive than in Iris, the inner segments generally spreading falcately with the outer ones. Filaments usually-joined in the lower part, sometimes entirely free. Many species. All plants of the Cape.

V. Ilelixyra. — Exactly Morrea, except that there is a long tube between the ovary and perianth-segments. One species. Cape.

VI. Vieusscuxia.^Wi^ Peacock Irises of the Cape. Root-stock a tunicated bulb ; tube above the ovary none ; inner segments of perianth minute, erect, usually with a distinct claw and three distinct cusps ; flowers fugitive ; filaments united up to the very top. Six or eight species, all Cape.

If Iris be divided at all I think these are the most satisfactory subordinate genera. Both in Liliacece and Iridacea; it is a great help to the memory to be able to marshal the genera into a bulbous and non-bulbous series, and if we use this subdivision, Iris and Uietes go into the second, and Xiphion, Morcer, Helixyra, and Vieusseuxia represent them amongst the bulbs ; but, as I have already indicated, there is really no clearly defined line of limit in lloral structure between the six. But many recent authors go still further in the way of subdivision. Iris, as above characterised, answers to four of the genera of Dr. Klatt's monograph — Oncocyclus,[Neubeckia, Ilermodactylus, and Iris ; and Xiphion to three — Xiphion, Coresanthe, and Gynandriris. In this present paper I intend to use Iris and Xiphion in the sense indicated above, and to confine my synopsis to these two, of which the species now known are not far short of a hundred.

Sub-genera of Xiphion and Iris. — The following are the groups or sub-genera, very unequal in size, under which I intend to arrange the species :^ <

Genus Xiphion of Tournefort and Miller.
Section 1. Euxiphion. — Inner segments of the perianth erect, nearly as long as the outer ; filaments free. Examples — X. vulgare, X. latifolium, X. reticulatum.
Section 2. Gynandriris.^lxwizx segments of the perianth erect, nearly as long as the outer ; filaments loosely joined to one another and the style. Example — X. Sisyrinchium.
Section 3. p/^;?!?. — Inner segments of perianth minute, spreading horizontally between the claws of the outer ones. Examples— X. persicum, X. caucasicum.

Genus Iris of Tournefort and Linn^us.
Section 1. Hcrmodacfylus.—Owiet segments of the perianth, or, as Miller calls them, '* falls," neither bearded nor crested ; root-stock a digitate tuber. Example— I. tuberosa.
Section 2. Apogon. — Falls neither bearded nor crested. Examples— I. Pseud-Acorus, I. laevigata, I. sibirica.
Section 3. Oiicocyclits.^YaX\?> hairy on the surface but not regularly bearded. Examples — I. susiana, I. iberica.
Section 4. /'i7«'t7/;/r/j, — Falls bearded down the claw. Examples — I, pumila, I. florentina, I. germanica.
Section 5. Evansia.—YaS\^ crested down the claw. Examples — I. cristata, I.japonica, I. tectorum.
Section 6. Hcxapogon.^QM\.fix and inner segments of the perianth both bearded down the claw. Examples — I, filifolia, I. falcifolia.

In distinguishing the groups and species the following are the principal points to which attention should be directed : — Root-stock, — The difference between a rhizome and tunicated bulb furnishes the most tangible difference between Xiphion and Iris, as here understood. In Xiphion, as in Crocus, the nature of the tunics, whether membranous or fibrous, furnishes a good mark of distinction. Compare, for instance, in this respect X. reticulatum with X. vulgare. In Iris only I. tuberosa stands out from the rest by its digitate tuberous root-stock.

Z^jcW. —There are three principal types of leaf — the narrow tetragonal type, shown in Iris tuberosa and Xiphion reticulatum ; the linear type, shown in Iris sibirica and prismatica ; and the sword-shaped or ensiform type, as shown in Iris Pseud-Acorus and germanica.

Stems. — A small set of species have no leaves to the stem, but the great mass are furnished with leaves on the stem, like those of the basal rosette reduced below the spathe- valves. Iris pumila and a few others never produce more than a single flower from a stem, but the great majority of the species have a forked corymbose inflorescence and two or many flowers.

Sfathe-vali'es.—'X\v^ spathe-valves are always at least two-valved, and greatly altered in shape and texture from the original foliar type. Their shape and texture furnish often good specific characters.

Flmver.—XX. is in the perianth that the main distinctive characters of the different kinds are to be found. In the structure of the ovary all the kinds are substantially alike. The absence or presence of a tube above the ovary, and its length, and the proportion it bears to the segments, is a point to be carefully noticed. The segments are always six in number, in two rows of three each. The outer three are always reflexed when the flower expands, in shape obovate, with a distinct claw, and nearly always larger than the three inner ones. The best differential character in the genera is furnished by the way in which these three outer segments are decorated down the claw and the keel of the lower part of the face. Sometimes, as in Iris tectorum and cristata, they have a distinct petaloid crest ; sometimes, as in Iris germanica and florentina, a keel of dense hairs, which is called in the descriptions a beard ; sometimes, as in Iris Pseud-Acorus and spuria, neither crest nor beard. Miller calls the three outer reflexing segments of the perianth "falls," and the three inner ones, which, in all the plants with which we are concerned, except the section Juno of Xiphion, stand straight up in the fully-expanded flower, "standards;" and, although these terms have been little used by later writers, they are so convenient and expressive that I should like to revive them again, and intend to use them in my descriptions. Mr. Barr at my suggestion has used them in this sense for the last two or three years in his catalogues.

Stigmas and Stamens. — It is not necessary for me to take up space here by describing the peculiar structure of the stigma, but I often find that gardeners who have a fair knowledge of botany do not understand the organography of an Iris flower— which parts are floral wrappers and which reproductive organs. I need scarcely say that any one who wants to understand these plants ought to begin at the very outset by getting clear ideas upon this head. The very special form of the stigma is uniform through both Xiphiun and Iris, though there is considerable modification in the size and shape of its two crests.

Ovary and Fruit. — The capsules often furnish good specific marks by size and shape, and this set of characters has been greatly overlooked. A set of drawings of Iiis capsules [and seeds] made from fresh specimens would be a useful contribution to our knowledge of the genus. J. G. Baker,

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