Hymenasplenium ngheanense Li Bing Zhang, K.W. Xu & N.T.Lu, 2018

Hymenasplenium ngheanense Li Bing Zhang, K.W. Xu & N.T.Lu View in CoL , sp. nov. Figs. 6 View FIGURE 6 , 7 View FIGURE 7 .

Type:— VIETNAM. Nghệ An: Con Cuong District, Chau Khe Commune, Khe Choang: Pu Mat National Park , 18°57’21.70”N, 104°38’39.62”E, elev. 400 m, 28 October 2014, Li Bing Zhang, Liang Zhang & Lu Thi Ngan 7163 (holotype CDBI! GoogleMaps , isotypes MO! GoogleMaps , VNMN! GoogleMaps ).

Diagnosis:— Hymenasplenium ngheanense is most similar to H. apogamum in having stipes brown and pinnae spreading or deflexed at base, entire at tooth margins, and usually crispate at base auricle, but the former has pinnae falcate or lanceolate, pinna apex acute or acuminate, while the latter has pinnae quadrangular-trapeziform, pinna apex obtuse to subacute.

Plants perennial, evergreen, 22–30 cm tall. Rhizomes short creeping, ca. 1–1.5 mm in diam., apex scaly, scales dark brown, lanceolate, margins nearly entire, 0.2–0.5 × 1.5–1.8 mm; root yellowish brown when dried, up to 8 cm long, ca. 1 mm diam, with yellow woolly indument or subglabrous. Fronds remote, 5–8 mm apart, herbaceous; petioles shiny, dark brown, 10–15 cm long, ca. 1 mm in diam., base sparsely covered with scales, scales lanceolate, castaneous, margins nearly entire, 0.2 × 1 mm, and covered with yellow woolly indument, or subglabrous. Laminae narrowly ovate or rarely narrowly triangular, 1-pinnate, 10–20 × 4.5–6 cm, widest near base, gradually narrowing toward apex, apex acuminate; rachises 0.5–1 mm in diam., subglabrous, shiny and castaneous abaxially, adaxial side grooved and with 2 green narrow wings. Pinnae almost sessile to shortly stalked, 12–20 pairs, alternate, lower pinnae deflexed toward stipe, falcate or lanceolate, (middle pairs) 2–3 × 0.4–0.8 cm, about 1– 0.6 mm apart, base asymmetrical, acroscopic side truncate and subparallel or forming an angle less than 15° with rachis, subauriculate, basiscopic side cuneate, with 4–12 mm absent (calculated from the base to the first tooth appearing in the margin of basiscopic side), acroscopic margins sinuate to serrate, teeth shallow and obtuse, not retuse, basiscopic margins entire at base, sinuate to serrate in the middle and apex; pinnae apex acute or acuminate. Veins visible on both sides of pinnae, green, rarely brown near pinnae petioles, lateral veins visible abaxially but obscure adaxially, forking and terminating in marginal teeth, only 1 or 2 basal basiscopic veins lacking. Sori linear, 2–4(–5) mm long, medial, (1–)4–8(–10) on acroscopic side and (1–)3–6 on distal basiscopic side of the pinnae in the middle part of the laminae, centers 1.5–2(–5) mm apart from one another; indusia stramineous, linear, membranous, entire, the indusium of the second sorus on the acroscopic side of pinnae opening toward rachis or absent, other indusia opening toward costa.

Geographical distribution:— Hymenasplenium ngheanense is currently only known from central and northern Vietnam.

Ecology:— Hymenasplenium ngheanense was observed to grow on wet rocks in humid and shady conditions of broad-leaved forest.

Etymology:—The species epithet is based on the name of Vietnamese province Nghệ An, and the Latin suffix, -ense, of origin, referring to the type locality of the new species.

Vernacular name:— XȐůďäffǎ (yi an mo ye tie jiao jue).

Taxonomic notes:— Hymenasplenium ngheanense , H. apogamum , and H. distans share some morphological similarities such as pinnae spreading or deflexed at base, entire at tooth margins, and usually crispate at base auricle. However, they are strongly supported as distinct lineages in our molecular study ( Xu et al. 2018a).

Additional material examined:— VIETNAM. Phu Tho: Tan Son District, Xuan Son National Park, 26 November 2013, Li Bing Zhang, Liang Zhang & Lu Thi Ngan 6532 (CDBI!, MO!, and VNMN!).