An evergreen shrub up to 20 ft high in the wild; young shoots and leaf-stalks very sticky with glandular bristles. Leaves oblong-lanceolate to oblanceolate, tapered to a narrow, often rounded base, slenderly pointed, 3 to 7 in. long, 3⁄4 to 13⁄4 in. wide, dark glossy green and soon glabrous above; clothed beneath with a soft tawny felt, with many small, ultimately dark glands on the midrib; leafstalk 5⁄8 in. long. Flowers about twelve in a truss. Calyx deeply five-lobed, the lobes narrowly oblong, 1⁄4 in. long, glandular-bristly and hairy like the flower-stalks which are up to 1 in. long. Corolla bell-shaped, 11⁄2 in. long, five-lobed, white with a dark blotch at the base and sometimes flushed with rose. Stamens ten, downy at the base. Ovary thickly furnished with stalked glands; style glabrous except at the base. Bat. Mag., t. 9464. (s. Barbatum ss. Crinigerum)
R. crinigerum was discovered by the French missionary Soulié in 1895 on the Mekong-Salween divide and introduced by Forrest in 1914. It seems to be a fairly common species in the Yunnan-Tibet borderland, from the Kari pass on the Mekong-Yangtse divide westward to the upper Irrawaddy, and all the sendings by Forrest and Dr Rock are from this region. But Kingdon Ward later found it as far west as the Delei river in the Mishmi Hills, Assam (KW 7123). It bears some resemblance to R. glischrum and R. habrotrichum in its flowers, but the dense, velvety covering beneath the leaf distinguishes it.
R. crinigerum is a very handsome species at its best, and is represented in the Windsor Great Park collection by a fine group of plants raised from KW 7123 and from various seed collections by Forrest and Rock. The material figured in the Botanical Magazine is from Rock 59186, collected on Mt Kenichunpu, Irrawaddy-Salween divide. R. crinigerum received an Award of Merit in 1935, when shown from Exbury on April 30.
var. euadenium Tagg & Forr. – Indumentum thinner, not completely concealing the undersurface of the leaf. There is a very striking example of this variety in the Windsor collection, raised from Rock 03908, with leaves about 9 in. long.
R. bainbridgeanum Tagg & Forr. – Leaves on the average shorter and relatively wider, much less pointed at the apex, otherwise not differing much from R. crinigerum. Introduced by Forrest in 1922 from the Tsarong region of S.E. Tibet, where it occurs on the Salween-Irrawaddy divide. Seeds collected later by Rock are from the same area.
From the Supplement (Vol. V)
R. bainbridgeanum – Tagg and Forrest, the authors of this species, considered it to be very closely allied to R. crinigerum, differing in the relatively much broader leaves less pointed at the apex, the thinner indumentum and the less rugose upper surface. But its proper place is in subsect. Selensia (Rev. 2, pp. 277 and 459). See also R. habrotrichum in this supplement.