白桫椤 bai suo luo

Alsophila brunoniana Wallich ex Hooker, Sp. Fil. 1: 52. 1844; A. contaminans Wallich ex Hooker var. brunoniana (Wallich ex Hooker) Scott; A. contaminans var. inermis Kurz; A. sollyana Griffith; Cyathea brunoniana (Wallich ex Hooker) C. B. Clarke & Baker; C. hainanensis Ching; Sphaeropteris hainanensis (Ching) R. M. Tryon.

Trunk erect, up to 10-20 m tall, up to 20 cm in diam. Stipe and rachis yellowish to purplish, smooth, or finely warty at base; scales pale brown or brown, thin, with setiferous edges; lamina 2-pinnate-pinnatifid, 2-3 × to 1.6 m; pinnae 20-30 pairs, ascending, lanceolate; largest pinnae up to 90 × 25 cm; pinnules narrowly lanceolate, 9-14 × 2-3 cm, slightly narrowed at base, apex caudate, pinnatifid to pinnatisect; pinnule segments 16-25 pairs, falcate, 10-16 × 3-5 mm, wider at base, entire or minutely crenate, rarely with small segments; veins 2- or 3-forked; abaxial side of pinnules glabrous, adaxial side glabrous or with sparse hairs; lamina glaucous abaxially; adaxial side of pinna rachis with pale antrorse hairs, a few pale hairs and scales along costules abaxially. Sori close to midveins of fertile pinnule segments, often throughout lower lamina; paraphyses pale to brown, filamentous, longer than sporangia or equal in length; indusia absent.

Evergreen forests in valleys; 500-1200 m. Hainan, Xizang, Yunnan [Bangladesh, India (N Himalaya), Myanmar, Nepal, Vietnam].

A very similar species, Sphaeropteris glauca (Blume) R. M. Tryon (syn. Cyathea contaminans Wallich ex Hooker), is mysteriously absent from China and is widely distributed from N India, Thailand, and Laos to New Guinea and the Philippines. The obvious difference is the stipe, rachis, and rachillae of S. glauca are prominently spiny (vs. smooth or only finely warty at the stipe base in S. brunoniana).