4. Aleuritopteris pygmaea Ching in S. K. Wu, Acta Phytotax. Sin. 19: 61. 1981.
矮粉背蕨 ai fen bei jue
Rhizomes ascending, short; scales bicolorous, dark brown with light brown margins, lanceolate. Fronds clustered. Stipe reddish brown, 1-2 cm, densely covered with concolorous brown scales and fibrous, twisted hairs, these extending onto rachis and costae. Lamina ovate, 1.3-1.5 × ca. 1 cm, bipinnatifid, papery when dry, abaxially with snow-white farina and sparse hairs, adaxially glabrous. Pinnae 3 or 4 pairs, opposite, slightly oblique upward; basal pair of pinnae widely separated from adjacent one, ca. 0.6 cm, pinnatipartite; ultimate segments 3 or 4 pairs, obliquely spreading, basal basiscopic segment larger, entire; second pair of pinnae subequal to or slightly longer than basal one, base decurrent or not. Veins obscure. Sori sparse, discontinuous, consisting of 2 or 3 sporangia. False indusia continuous, narrow, margins entire.
● Rock crevices in valleys; 3800-3900 m. Xizang.
Aleuritopteris pygmaea is the smallest species in the genus. It is distinguished from other species by its reddish brown stipe, which is densely covered with scales and twisted, long hairs.
We have not seen material of Aleuritopteris mengshanensis F. Z. Li (Acta Phytotax. Sin. 22: 153. 1984), described from Shandong. It appears to be most closely related to A. pygmaea but without the twisted hairs on the stipe.