线叶石斛 xian ye shi hu

Aporum rivesii (Gagnepain) Rauschert; Callista aurantiaca Kuntze; Dendrobium aurantiacum H. G. Reichenbach (1887), not (F. Mueller) F. Mueller (1870); D. aurantiacum var. zhaojuense (S. C. Sun & L. G. Xu) Z. H. Tsi; D. chryseum var. bulangense G. X. Ma & J. Xu; D. clavatum Wallich ex Lindley var. aurantiacum Tang & F. T. Wang; D. flaviflorum Hayata; D. rivesii Gagnepain; D. rolfei A. D. Hawkes & A. H. Heller; D. tibeticum Schlechter; D. zhaojuense S. C. Sun & L. G. Xu.

Stems cylindric, usually 25-35 cm, slender, 2-4 mm in diam., unbranched, with many nodes, internodes 2.5-4 cm, pale yellow or yellowish brown when dry. Leaves linear or narrowly oblong, 8-10 × 0.4-1.4 cm, leathery, base sheathing, apex obtuse and emarginate or sometimes subacute and obliquely hooked; leaf sheath tightly embracing stem. Inflorescence lateral on old leafless stem, ca. 1 cm, usually 1 or 2(or 3)-flowered; peduncle suberect, ca. 0.5 cm; basal sheaths 3 or 4, overlapping, pale white, cupular or tubular, papery, basal ones short, distally elongate, 5-20 mm; floral bracts pale white, cymbiform, 12-13 × ca. 5 mm, membranous, apex obtuse. Pedicel and ovary ca. 3 cm. Flowers spreading, ca. 6.5 cm wide, concolorous yellow, center a darker shade, occasionally with large purple spots on sepals and petals and a purple spot on lip disk, inner surface of lip sometimes with several red stripes. Dorsal sepal oblong-elliptic, 23-25 × 11-14 mm, 5-veined, obtuse; lateral sepals slightly obliquely oblong, ca. as long as dorsal sepal or slightly narrower, 5-veined, apex obtuse; mentum conic, ca. 6 mm. Petals elliptic or broadly elliptic-obovate, 24-26 × 14-17 mm, 3-veined, lateral major veins branched, apex obtuse; lip suborbicular, ca. 25 × 22 mm, adaxially densely pilose, both sides embracing column below middle, claw ca. 3 mm, margin irregularly denticulate, disk without markings. Column ca. 4 mm, foot ca. 3 mm; anther cap narrowly conic, ca. 4 mm, glabrous, apex subtruncate. Fl. May-Jun. 2n = 38.

Epiphytic on tree trunks in high-mountain broad-leaved forests; 1700-2600 m. C Sichuan (Ebian, Emei Shan), Taiwan, NW to SE Yunnan [NE India, Myanmar].

Dendrobium chryseum has been more widely known as D. aurantiacum H. G. Reichenbach but that name is illegitimate because it is a later homonym. Plants from 1700-1800 m in C and S Sichuan and Yunnan with pale purple markings on the sepals and a purple spot on the lip disk have been referred to D. aurantiacum var. zhaojuense.

Seidenfaden (Opera Bot. 83. 1985) united two distinct entities under Dendrobium chryseum, namely D. chryseum and D. denneanum (see below).