3. Betula cylindrostachya Lindley in Wallich, Pl. Asiat. Rar. 2: 7. 1831.
长穗桦 chang sui hua
Betula acuminata Wallich var. cylindrostachya (Lindley) Regel; B. alnoides Buchanan-Hamilton var. cylindrostachya (Lindley) H. Winkler; Betulaster cylindrostachya (Lindley) Spach.
Trees to 30 m tall; bark brown or grayish black. Branchlets yellow-brown, densely yellow villous. Petiole 0.8-1.5 cm, densely yellow pubescent; leaf blade ovate-elliptic, oblong, or ovate-lanceolate, 5-14 × 2-8 cm, both surfaces densely villous when young, abaxially densely resinous punctate and bearded in axils of lateral veins, base rounded or subcordate, margin irregularly and doubly subincurved setiform serrate; apex acuminate; lateral veins 13 or 14 on each side of midvein. Female inflorescences 2, narrowly cylindric, 2.5-10 cm × 5-7(-10) mm; peduncle 7-10 mm, densely yellow pubescent; bracts oblong-lanceolate, 2-3 × 1.5-1.7 mm, sparsely pubescent at base, ciliolate, spongy at base when mature, 3-lobed, middle lobe ovate-lanceolate, lateral lobes ± reduced, ca. 1/3 as long as middle lobe. Nutlet ovate or oblong, ca. 2 × 1-1.5 mm, densely pubescent at apex, with membranous wings ca. 2 × as wide as nutlet. Fl. Apr-Jun, fr. Jul-Aug. 2n = 28.
Subtropical and warm temperate broad-leaved forests; 1400-2800 m. ?Sichuan, SE Xizang, NW Yunnan [Bhutan, India]