锡金枫 xi jin feng

Acer hookeri Miquel; A. hookeri var. normale Schwerin; A. hookeri var. orbiculare W. P. Fang & Y. T. Wu; A. medogense T. Z. Hsu & Z. K. Zhou; A. pluridens T. Z. Hsu & H. Sun; A. sikkimense subsp. hookeri (Miquel) Wesmael; A. sikkimense var. serrulatum Pax; A. sikkimense var. subintegrum Schwerin.

Trees to 20 m tall, andromonoecious. Bark black-gray. Branchlets brown, glabrous; winter buds ellipsoid, large, scales 4 pairs, glabrous. Leaves deciduous; petiole 2-4 cm, glabrous, leaf blade abaxially pale green, adaxially dark green, ovate or ovate-oblong, 10-14 × 5-8 cm, papery, abaxially with barbed hairs at vein axils when young, glabrescent, adaxially glabrous, base subcordate or nearly rounded, undivided, margin entire or nearly entire, sometimes serrulate, apex caudate. Inflorescence terminal, racemose, 40-50-flowered. Pedicel ca. 2 mm, glabrous. Sepals 5, oblong-ovate, ca. 3 mm, apex obtuse. Petals 5, yellowish green, ca. as long as sepals. Stamens 8, glabrous, rudimentary in pistillate flowers; anthers pale yellow. Disk glabrous, intrastaminal. Ovary glabrous; style very short; stigmas widely spreading. Fruit brownish when mature; nutlets flat, ovate-oblong, ca. 8 × 5 mm; wing falcate, including nutlet 2-2.5 cm × ca. 8 mm, wings spreading obtusely, rarely horizontally. Fl. Mar, fr. Sep. 2n = 26.

Mixed forests; 1700-3000 m. SE Xizang, Yunnan [Bhutan, N India, N Myanmar, Nepal].