Hymenophyllum chamaecyparicola T.C.Hsu & Z.X.Chang, 2022

Chang, Zhi-Xiang, Hsu, Tian-Chuan & Kuo, Li-Yaung, 2022, Hymenophyllum chamaecyparicola (Hymenophyllaceae), a new filmy fern species from Taiwan, PhytoKeys 204, pp. 23-34 : 23

Hymenophyllum chamaecyparicola T.C.Hsu & Z.X.Chang sp. nov.

Figs 1 , 2

Type.

Taiwan. Yilan County: Datong Township, Mingchih , 1200-1300 m, 31 January 2019, Z.X. Chang ZXC01438 (holotype: TAIF; isotype: TAI) .

Diagnosis.

Morphologically, Hymenophyllum chamaecyparicola is most similar to H. wrightii in sharing pinnate to bipinnatifid fronds, entire segment margins, and bivalvate, entire or subentire involucres. However, the new species could be clearly distinguished from H. wrightii by the presence of minute spathulate hairs on both surfaces of laminae (vs. glabrous laminae in H. wrightii ) (Fig. 1H, I ), the lack of two veinlets at the base of sori (vs. two veinlets at the base of sori in H. wrightii ), and sori confined to apex or upper margins of laminae (vs. on short acroscopic segments close to rachis in H. wrightii ) (Fig. 1J ). This new species is phylogenetically related to H. barbatum , H. devolii , H. exsertum , H. okadae and H. oligosorum , while it could readily be distinguished from H. barbatum , H. devolii and H. okadae in having entire (vs. serrate) segment margins (Fig. 1D-G ) and from H. exsertum and H. oligosorum in having pinnatifid to bipinnatifid (vs. bipinnatifid to tripinnatifid) laminae (Fig. 1D-G ) sparsely covered with short (<0.2 mm) clavate hairs (vs. densely covered with> 1 mm long acicular hairs) on abaxial surface of rachis and costae (Figs 1H, I , 2E ).

Description.

Plants epiphytic. Rhizomes long creeping, blackish brown, 0.2-0.3 mm in diam, covered with caducous golden brown multicellular hairs, turning glabrescent when aged. Fronds (1)3-7(10) mm apart, (0.7)1-2.5(4.5) cm long, usually pendent. Stipes dark brownish, (1)2-12(25) mm long, ca. 0.15 mm in diam., wingless, with very sparse caducous hairs similar to those on the rhizomes, turning glabrescent when aged. Laminae pinnatifid to bipinnatifid, flabellate-orbicular, ovate or elliptic, (0.8)1-2.2(3.5) × (0.4)0.6-1.1(1.5) cm, membranous, base obtuse, apex rounded, with minute pale brownish clavate hairs along both surfaces of rachis, costae and veins, otherwise glabrous; clavate hairs up to 0.15 mm long, very sparse adaxially, sparse to scattered abaxially; rachises brown, slightly zigzag, winged throughout or sometimes wingless at base, wings up to ca. 0.2 mm wide, flat, entire; pinnae 2-4(5) pairs, alternate, forming acute angles with rachis, lower pinnae usually forked, rarely more dissected, upper pinnae usually simple, (2)3-8(11) mm long; ultimate segments oblong, (1)2-7(10) × 1.2-1.5 mm, apex rounded, entire, flat or slightly involute; veins simple, greenish brown, ending slightly below the apical margin. Sori 1-3(6) per lamina, confined to apex of lamina or sometimes scattered along upper margins, solitary and terminal on ultimate segments, segment lamina usually slightly constricted below sori; involucres bivalvate, orbicular, ovate-orbicular or elliptic, 1.2-2 × 1-1.5 mm, with a few minute clavate hairs at base, margins entire or minutely erose; receptacles inserted. Spores chlorophyllous, 64 per sporangium.

Additional specimen examined.

Taiwan. Yilan County: Datong Township, Mingchih, 1200-1300 m, 11 February 2019, Chang ZXC01440 (TAIF); same loc., 11 July 2019, Chang ZXC01670 (TAIF); same loc. and date, Hsu 11888 (TAIF).

Distribution and habitat.

Hymenophyllum chamaecyparicola is endemic to Taiwan and currently known from scattered populations on a single ca. 2000 m2 mountain slope in Chamaecyparis montane mixed cloud forest ( Li et al. 2013) around Mingchih (24.65361°N, 121.46950°E). It is epiphytic on bases of tree trunks and exposed roots of Chamaecyparis obtusa var. formosana (Hayata) Hayata.

Etymology.

The specific epithet, a noun in apposition, is derived from Chamaecyparis , a Gymnosperm genus, and - cola, dweller, alluding to unusual habitat of the new species occurring on the lower trunk of the giant C. obtusa var. formosana .

Figures

Figure 1. Habitat and morphology of Hymenophyllum chamaecypericola, from Hsu 11888 (TAIF) A, B wild population growing on moss-covered basal trunk of a giant Chamaecyparis obtusa var. formosana C rhizome and young frond, showing the wingless and scarcely hairy stipe D-G fronds, adaxial views (D, E) and abaxial views (F-G) H, I laminae, adaxial view (F) and abaxial view (G), showing the minute yellow-brown clavate hairs on rachis and veins. J. Sori. Scale bars: 2 cm (B); 5 mm (C, J); 1 cm (D-G); 2 mm (H, I).

Figure 2. Line drawing of Hymenophyllum chamaecypericola T. C. Hsu & Z. X. Chang, sp. nov., based on the holotype Z. X. Chang ZXC 01438 (TAIF) A rhizome and fronds B sterile frond C fertile frond D sori E a clavate hair.