37. Acer calcaratum Gagnepain, Notul. Syst. (Paris). 13: 192. 1948.
三裂枫 san lie feng
Trees small, to 7 m tall, andromonoecious, deciduous. Branchlets smooth, green and glabrous, greenish brown or olive-brown in second year; winter buds ovoid, 4-paired. Petioles 1.5-4.6 cm, glabrous; leaf blade abaxially light green, adaxially olive green, 6-15 × 5-21 cm, papery, deeply 3-lobed, base rounded, rarely subcordate, abaxially reticulate and glabrous except for axillary tufts of pale hairs; lobes triangular-ovate, margin entire, apex acuminate; main veins 3, developing from leaf base, main veins and veinlets distinct on both surfaces. Inflorescence corymbose, terminal on a 2-leaved branchlet. Sepals 5, purplish red. Petals 5, white. Stamens 8. Disk glabrous, extrastaminal. Styles 2. Samaras glabrous; nutlets brown, ovoid, ca. 5 × 7 mm, distinctly veined; wings spreading obtusely, wing including nutlet 4-6 × 1.4-1.7 cm, reddish when young, brownish when mature; pedicel 1.7-2 cm, glabrous. Fl. Nov-Jan, fr. Mar-Jul.
Scattered by streams in rain forests; 1200-2400 m. S Yunnan [Myanmar, Thailand, Vietnam].
This is a new record and a very rare maple in China.