Loxogramme yigongensis Ching & S. K. Wu (1983: 351)

Yang, Jian-Jun, Wan, Xia, Zhao, Wang-Lin, Liang, Zhen-Long & Zhang, Liang, 2022, Reinstatement of Loxogramme yigongensis (Polypodiaceae), an endemic species from southeastern Xizang, China, Phytotaxa 555 (1), pp. 95-102 : 99-100

Loxogramme yigongensis Ching & S. K. Wu (1983: 351) , Fig. 1

Type:— CHINA. Xizang: Bomi County, Yigong Xiang , elev. 2000 m, in dense forests, 15 July 1965, T.-C. Yin & D.-Y. Hong 0598 (holotype, PE-01185170 !; isotypes, PE-01185166!, PE-01185167!, PE-01185168!) .

Description: —Plant small, 8–15 cm. Rhizome long creeping, slender, ca. 0.5–1.1 mm in diam., densely covered with scales; scales lanceolate, brown, ca. 1.1–1.5-1.2 × 0.3–0.6 mm, margins slightly dentate. Fronds closely spaced or distant, monomorphic; stipe very short or indistinct; lamina simple, succulent, spongy adaxially and abaxially, becoming rugose on both surfaces when dry, 7–14 × 0.5–1.0 cm, widest near middle, apex acute, base gradually narrowed and decurrent; costa obviously raised adaxially, slightly raised abaxially; veins hidden, anastomosing. Sori 3-6 pairs, ca. 10–20 ° from costa, confined to middle-upper part of lamina, 3–12 × 1–1.5 mm, elongate, close and subparallel to costa, slightly sunken; one sporangium with 64 spores when mature. Spores globose, small tuberculate, trilete.

Distribution and habitat: — Loxogramme yigongensis is narrowly distributed in southeastern Xizang, China. Presently only five populations are known to us, including one population rediscovered near the type locality in Yigong Xiang of Bomi County, and four newly discovered populations in Beibeng Xiang and Bangxin Xiang of Medog County. It grows on old tree-trunks or rocks in primary forests, at elevations between 2200 and 2600 m. High humidity is necessary for the growth of the species.

IUCN Red List category:—EN-ENDANGERED (CR B1ab(iii) + D) following the IUCN (2021) criteria: five populations on rocks or tree trunks with about 280–320 plants in total was observed in the field.

Additional specimens examined: — CHINA. Xizang: Bomi County, Yigong Xiang, elev. 2500 m, on rocks in broadleaved evergreen forests near a large river, 15 June 2021, L. Zhang, X. Wan & J.- J. Yang 4105 ( KUN, PYU); Medog County, Beibeng Xiang , elev. 2000 m, on a tree trunk in broadleaved evergreen forests near a large river, 16 October 2017, L. Zhang, W.- B. Ju & H.- N. Deng 2130 ( KUN); Medog County, Bangxin Xiang , elev. 2600 m, on an old tree-trunk in broadleaved evergreen forests of primary vegetation, 17 June 2021, L. Zhang, X. Wan & J.- J. Yang 4169 ( KUN, PYU) .

Figures

FIGURE 1. Loxogramme yigongensis.—A. Habit.—B. Adaxial lamina.—C. Portion of abaxial lamina showing sori.—D. Rhizome.—E. Rhizome scale.—F–H. Spores (Scale bars: E. 0.5 mm; F. 0.5 µm; G–H. 10 µm).