无毛肿足蕨 wu mao zhong zu jue

Plants ca. 35 cm tall. Rhizomes short, densely scaly together with swollen stipe base; scales reddish brown, lustrous, lanceolate, ca. 1.5 cm × 1-1.5 mm, membranous. Fronds subclustered; stipe stramineous, 12-15 cm × 1.5-2 mm, glabrous; lamina pentagonal-ovate, ca. 20 × 15 cm, herbaceous, glabrous or sparsely hairy along rachis, costae, and veins adaxially, base cordate, 4-pinnate, apex acuminate and pinnatifid; pinnae ca. 8 pairs, slightly oblique, stalked, lower 1 or 2 pairs opposite, 4.5-5.5 cm apart, upper pairs alternate or subopposite; basal pair largest, triangular-lanceolate, ca. 11 × 7 cm, base subrounded, stalk ca. 1 cm, 3-pinnate, apex acuminate; pinnules ca. 10 pairs, anadromous, alternate, oblique, shortly stalked, acroscopic ones smaller, proximal basiscopic pair largest, oblong, ca. 5 × 3 cm, base cordate, asymmetrical, 2-pinnate, apex acuminate; ultimate pinnules 4 or 5 pairs, basal one ca. 5 × 3 mm, shallowly pinnatifid or undulate; segments with 1 or 2 crenations at apex; second and upper pairs of pinnae gradually shorter, oblong-lanceolate, base cordate or broadly cuneate, apex acuminate. Veins obvious on both surfaces, pinnate, ending at margin. Sori small, orbicular, 1 per segment, located at middle of veinlets; indusia pale gray, reniform, medium-sized, glabrous.

● Limestone rock crevices on sunny slopes; ca. 1800 m. S Yunnan (Yuanmou).

Hypodematium glabrum is similar to H. hirsutum but is distinguished by its small stature and glabrous fronds.