27. Diplazium prolixum Rosenstock, Repert. Spec. Nov. Regni Veg. 13: 126. 1913.
双生双盖蕨 shuang sheng shuang gai jue
Allantodia prolixa (Rosenstock) Ching.
Plants evergreen, large. Rhizome creeping, brown, ca. 1.5 cm in diam., apex densely scaly; scales slightly shiny, linear-lanceolate, ca. 1 cm, 1-1.5 mm in diam., thickly membranous, entire, filiform at apex, slightly curly; fronds approximate. Fertile fronds up to 2 m; stipe brown at base, upward green-stramineous, up to 1 m, up to 7 mm in diam., base with dense linear-lanceolate brown scales, upper part glabrous, shallowly grooved adaxially; lamina 2-pinnate with pinnatipartite to pinnatisect pinnules, or base 3-pinnate, ovate-deltoid, up to 1 m × 80 cm, apex acuminate; pinnae up to ca. 18 pairs, lower pinnae subopposite; upper pinnae alternate, ascending, broadly ovate-lanceolate or oblong-lanceolate, up to 50 × 30 cm, slightly narrowed to base, base cuneate, stalk up to 6 cm, apex acuminate; pinnules up to ca. 15 pairs, alternate, broadly lanceolate or linear-lanceolate, up to 20 × 6 cm, slightly narrowed to base, base symmetrical, shallowly cordate, with stalk ca. 5 mm, apex long acuminate; secondary pinnules up to ca. 15 pairs, ascending, linear-lanceolate or oblong, up to 4 × 1.2 cm, sessile, pinnatifid to pinnatipartite, apex acuminate or acute to rounded; lobes of secondary pinnules up to 8 pairs, ascending, contiguous, oblong, up to 5 × 3 mm, sparsely thinly serrate, rounded or truncate at apex; veins not prominent, pinnate; veinlets 4 or 5 pairs per lobe, mostly simple, occasionally forked, ascending. Lamina herbaceous, gray-green or light green adaxially when dry, glabrous on both surfaces; rachis and costa stramineous, glabrous, shallowly grooved adaxially. Sori oblong, 1-3 pairs per lobe, subcostular-inframedial, single or double on basal veinlets; indusia light brown, thinly membranous, entire, vaulted when mature, usually irregularly ruptured. Spores hemispherical, perispore with irregular aculeate projections.
Sparse valley forests in limestone areas; 500-1600 m. Chongqing, Guangxi, Guizhou, Yunnan (Guangnan) [Vietnam].