Hymenasplenium quangnamense Li Bing Zhang, K.W. Xu & Liang Zhang, 2018

Xu, Ke-Wang, Zhang, Liang, Lu, Ngan Thi, Zhou, Xin-Mao, He, Hai, Luong, Thien Tam, Knapp, Ralf, Liao, Wen-Bo & Zhang, Li-Bing, 2018, Nine new species of Hymenasplenium (Aspleniaceae) from Asia, Phytotaxa 358 (1), pp. 1-25 : 15-17

Hymenasplenium quangnamense Li Bing Zhang, K.W. Xu & Liang Zhang , sp. nov. Figs. 10 , 11 .

Type:— VIETNAM. Quảng Nam: Song Thanh Nature Reserve, Nam Giang District, Ta Bhing Community, Ta Ding Village , 15°37’58.18”N, 107°44’17.86”E, elev. 200–350 m, 4 December 2014, Li Bing Zhang, Liang Zhang & Ngan Thi Lu 7884 (holotype CDBI! , isotypes MO! , VNMN! ).

Diagnosis:— Hymenasplenium quangnamense is most similar to H. apogamum in having rhizomes densely scaly, roots robust (ca. 1 mm in diam.), and pinnae quadrangular or trapeziform, but the former has marginal teeth at the base of pinnae often slightly retuse, veins terminating below notches, and sori supramedial to (sub)marginal, while the latter has marginal teeth at the base of pinnae entire, veins terminating in marginal teeth, and sori medial.

Plants perennial, evergreen, 25–40 cm tall. Rhizomes creeping, ca. 4 mm in diam., apex densely scaly, scales black, narrowly triangular or lanceolate, margins nearly entire, 2–3.6 × 0.4–0.7 mm; root yellow or yellowish brown when dried, robust, up to 10 cm long, ca. 1 mm diam, rhizome and root sparsely with yellow woolly indument or glabrous. Fronds remote, up to 8 mm apart, herbaceous; petioles slender, shiny, dark brown, glabrous, 8–20 cm long, ca. 1 mm in diam., base near rhizome sparsely covered with scales, scales lanceolate, black, margins nearly entire, 0.1–0.2 × 2–3 mm. Laminae narrowly ovate, 1-pinnate, 15–20 × 4.5–6.5 cm, base slightly reduced, widest near base, gradually narrowing toward apex, apex acute; rachises 0.5–1 mm in diam., glabrous, shiny, dark brown, adaxial side grooved and with 2 green narrow wings. Pinnae shortly stalked to almost sessile at apex, 15–20 pairs, alternate, quadrangular or trapeziform, (middle pairs) 2.5–3 × 0.5–0.8 cm, about 5–10(–15) mm apart, base asymmetrical, acroscopic side truncate and subparallel or forming an angle less than 15° with rachis, basiscopic side cuneate, with 10–15 mm absent (calculated from the base to the first tooth appearing in the margin of basiscopic side), acroscopic margins serrate, teeth not retuse, acute or obtuse, basiscopic margins entire at base, serrate in the middle and apex; pinna apex obtuse. Veins visible on both sides of pinnae, stramineous to green, rarely brown near pinnae petioles, lateral veins visible on both sides of pinnae, green, forking and terminating in marginal teeth, 2–3 basal basiscopic veins lacking. Sori linear, 2–5 mm long, supramedial to (sub)marginal, (1–)9–11 on acroscopic side and (2–)5–7 on distal basiscopic side of the pinnae in the middle part of the laminae, centers 1–2(–4) mm apart from one another; indusia brown, linear, membranous, entire, the indusium of the second sorus on the acroscopic side of pinnae opening toward rachis or absent, others opening toward costa.

Geographical distribution:— Hymenasplenium quangnamense is currently only known from Quảng Nam Province, central Vietnam. It is likely endemic to Vietnam.

Ecology:— Hymenasplenium quangnamense was observed to grow on rocks cave at an elevation of ca. 300 m with humid and shady conditions.

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

Vernacular name:— Ḟħůďäffǎ (guang nan mo ye tie jiao jue).

Taxonomic notes:— Hymenasplenium quangnamense is morphologically similar to H. apogamum . Our molecular analysis ( Xu et al. 2018a) did not well resolve its relationships but it had a very long branch length on the phylogenetic tree showing its isolated relationships in the genus.

Figures

FIGURE 10. Hymenasplenium quangnamense Li Bing Zhang, K.W. Xu & Liang Zhang.—A. Habitat and plants.—B.Abaxial lamina.— C. Adaxial lamina.—D. Sorus distribution.—E. Portion of adaxial lamina.

FIGURE 11. Hymenasplenium quangnamense Li Bing Zhang, K.W. Xu & Liang Zhang.—A. Habit.—B. Portion of abaxial laminae and sorus distribution.—C. Rhizome and scales.—D. Portion of adaxial lamina.