|The World Checklist accepts this as a natural hybrid name for crosses between Iris brevicaulis and Iris giganticaerulea|
|It appeared in the 1939 AIS Checklist as 'Flexicaulis' ( John Kunkel Small, 1927) Vinic-B; Addisonia 12: 1, March 1927 with colored plate; Oakhurst 1939|
| Addisonia 12: 1, March 1927 Small gave the following;
Native of the southcentral United States
The ratio of blue-flags of the hexagona group west and east of the Appalachians stands respectively two to one. The angle-pod blue-flag (Iris hexagona) , the eastern representative, is a very robust plant, in fact it is our most vigorous iris, and its few flowers are very large and of firm texture. The western representatives, the leafy blue-flag (Iris foliosa) and the one here illustrated, are less vigorous vegetatively, as for as rigidity is concerned. In fact the flower-stems are so weak that they promptly bend down or become prostrate, and although the flower-parts are more delicate, an abundance of flowers is produced, as one or two buds arise at each of the several nodes of the very zigzag stem. In contrast with the leafy blue-flag, the nearest relative of the species here illustrated, which produces leaves in abundance and size exceeding those of any of our blue-flags, those of Iris flexicaulis are scarcely as large as those of the common blue-flag (Iris versicolor) . The type specimens, collected along the Nueces River, Texas, by B. C. Tharp, are in the herbarium of The New York Botanical Garden. Plants of the original collection survived two winters in the cold frames at the Garden and the severe winter of 1925-26 in the beds of the iris plantation.
One would be inclined to assume a common ancestor for the species under consideration and Iris foliosa. Although they are abundantly distinct from each other in foliage, floral, and fruit characters, they are on the other hand more closely related to each other than to any other species. Among the gross differences, the superabundance of leaves is evident in the case of Iris foliosa – whence its specific name – while a superabundance of flowers seems to obtain in Iris flexicaulis.
The marsh and swamp, and sometimes the stream-bed, where the stream runs dry part of the year, are the natural haunts of this flag. A dense turf in a marshy slope, a tangle of willow roots and stems, and a soppy floor of a cypress-head are to the liking of this flag as a residence. In all its habitats the bright-violet colored flowers are conspicuous and they are individually more prominent by the mixture of yellow and white in the sepals. The pods are relatively rather ponderous. They early bend the supporting stalk to the ground, where the usual moisture soon causes the walls to decay and release the corky seeds.
Its exact geographic range, as in the case of most of our interior species, is not yet clear. It might be defined, however, without much chance of error, as the lower Mississippi watershed and the drainage basins of eastern Texas.
The zigzag-flag has a stoutish horizontal branching rootstock which is sometimes partly fibrous with the remains of spent leaves. The leaves are erect, mostly three or five together, pale green and more or less glaucous. The blades are linear-attenuate, mostly one half to three quarters of an inch wide. The flower-stalk is erect, stoutish or slender, shorter than the basal leaves, exceptionally leafy, glaucescent, with several short internodes placed at an angle, thus zigzag. The flowers are paired or three together at the top of the stem or sometimes solitary, and one, or two together, in the axils of the stem-leaves. The involucre has two main bracts, which are exceeded by the flower, not foliaceous. The pedicel is shorter than the ovary. The hypanthium surrounding the ovary is six-angled. The perianth-tube iscylindric-prismatic, nearly or quite a half inch long. The three sepals are broadly spatulate, two and a quarter to two and three quarters inches long, spreading or recurved at the tip. The blade is obovate, deep-violet except near the base, where the yellow-green striae and median crest extend up from the claw and pass into white fleck-like radii. The claw is about as long as the blade, less than a half inch wide, dull-green without, yellow-green, except the dark flecks on and between the ridges, within. The three petals are shorter than the sepals, narrowly spatulate, somewhat spreading. The blade is dull violet without, deep violet within, notched at the apex. The claw is greenish violet without, streaked with violet and brown within. The three stamens are an inch to an inch and an eighth long. The filament is greenish at the base, paler above. The anther is pale yellowish green, shorter than the filament. The three style-branches are two inches long or nearly so, nearly as long as the petals, broadly linear, reddish violet, except the paler margins. The style-appendages are scimitar-shaped, five eighths of an inch long, irregularly and bluntly toothed on one side, mostly so above the middle. The stigma is two-lobed. The capsule is oval or ellipsoid, varying to somewhat obovoid, two to three inches long, drooping, six-angled, pale green and more or less glaucous, with the angles prominent and sharp, the walls very thick. The seeds are borne in two rows in each capsule-cavity, half-circular, brown, corky.
John K. Small.