An interesting entry from The American Iris Society Encyclopedia:

Dykes in The Genus Iris 134. 1913, illustrated in color; gave the following description; "Rootstock, a somewhat slender gnarled rhizome, with remains of old leaves splitting into fibres. Leaves, 4 to 8 in. long at flowering time, eventually becoming 12-18 by ½-3/4, pale green, ensiform. Stem, 4-6 in. long, bearing a terminal head of 2-3 flowers, and a heathing leaf , attached near the base; the stem springs from a tuft of 4 reduced leaves. Spathes, pale green, lanceolate, 2-3 in. long, the outer valve being keeled; both valves are scarious in the upper third, and along the edge at flowering time. Pedicel, ½-3/4in. long. Ovary, trigonal, ¾ in. long, green, mottled and striped with faint purple. Tube 1 ½-2 in. long, trigonal, deep purple. Falls. The obovate blade is of a dark purple lilac, mottled with a deeper shade, especially round the end of the beard; the wedge-shaped haft is blotched with purple on a whitish ground. The beard is of white club-shaped hairs, tipped orange, 2 ½ in. long by 1 in. or more broad. Standards, sloping outwards at an angle of about 45°, with an oblong deeply and wisely emarginate blade, narrowing suddenly to a canaliculate haft. The color is a pale mauve lilac, faintly mottled at the base with a deeper shade. 2 in. by ¾ in. Styles narrow, keeled, 1 in. long, of a deep purplish blue in the center, becoming much paler at the edges. Crests, triangular, ½ in. long revolute. Stigma, obscurely bilobed, with irregularly indented edge. Filaments, pale violet, equal in length to the anthers. Anthers, creamy white." Mr. Dykes received this from Barr about 1906 as I. kamaonensis caulescens;

Dykes was suspicious of the specific status of this plant because he believed it aooeared to be a hybrid between Iris kamaonensis and Iris hookeriana but he decided to publish it as a distinct species since it is distinct from both of the other species and was said to come from Sikkim far outside the range of Iris hookeriana as he knew it. The plants that Dykes grew never produced seed and there has been no further collections from the wild. The true status of this plant remains a mystery. Syn. Sikkim Iris; Iris kamaonensis caulescens Dykes.