Etymology: From the Greek brachys, short, and acanthos, spine, referring to the characteristically short petiolar spines of this species. Historical notes: Discovered and recognised as a distinct taxon only in the 1990's. Distinguishing features: This species is one of the complex of closely related mostly acaulescent taxa with soft pollen cones, loose, freely peeling sarcotesta lacking a fibrous layer and rugose sculpting of the sclerotesta (Section Stangerioides) that is distributed through northern Vietnam, Laos, northern Thailand and Yunnan and Guangxi in southern China. Within that group, it is distinguished by the small stature and long leaves with long petioles and short petiolar spines, the very small pollen cones on long peduncles, the rounded microsporophylls which lack any apiculus and the small megasporophylls. The reduced megasporophylls suggest that C. brachycantha is nearest to C. hoabinhensis and C. chevalieri. Older plants develop a slender, often decumbent aerial trunk. Distribution and habitat: Known at present from a limited region in Bac Can province, Vietnam. Locally frequent although not in dense stands, on the crests of outcropping limestone ridges within closed evergreen forest canopy, growing in clefts and crevices in bare rock with no soil. Conservation status: Well represented within Ba Be National Park, and not considered to be at risk. IUCN (1994) status LR, nt.
Description:
Stems arborescent to acaulescent, to 1 m tall, 9-12 cm diam. at narrowest point; 5-10 leaves in crown. Leaves deep green, highly glossy, 140-250 cm long, slightly keeled to flat (not keeled) in section (opposing leaflets inserted at 160-180° on rachis), with 100-210 leaflets, with white tomentum shedding as leaf expands; rachis consistently terminated by paired leaflets. Petiole 50-90 cm long (35-45% of total leaf), petiole glabrous, spinescent for 90-100% of length. Basal leaflets not gradually reducing to spines, 150-200 mm long. Median leaflets simple, strongly discolorous, 200-250 mm long, 10-14 mm wide, inserted at 70-85° to rachis, decurrent for 6-8 mm, narrowed to 2.5-4 mm at base (to 20-30% of maximum width), 10-21 mm apart on rachis; median leaflets section flat; margins undulate; apex softly acuminate, not spinescent; midrib raised above, flat below. Cataphylls narrowly triangular, pungent, pilose, 50-80 mm long, articulated. Pollen cones fusiform, yellow, 12-14 cm long, 3-4 cm diam.; microsporophyll lamina soft, not dorsiventrally thickened, 12-15 mm long, 6-10 mm wide, fertile zone 10-12 mm long, sterile apex 2-3 mm long, level, apical spine absent. Megasporophylls 8-12 cm long, brown-tomentose; ovules 2-4, glabrous; lamina ovate, 25-40 mm long, 15-25 mm wide, deeply pectinate, with 14-22 soft lateral spines 15-25 mm long, 2.5 mm wide, apical spine not distinct from lateral spines. Seeds ovoid, 25-27 mm long, 20 mm wide; sarcotesta yellow, not pruinose, 1-2 mm thick; fibrous layer absent; sclerotesta verrucose. Spongy endocarp absent.
|
