Argyrochosma connectens (C.Chr.) G.M.Zhang, 2015

Wang, Wan, Yang, Wenli, Mao, Xingxing, Zhao, Ranran, Dou, Ping & Zhang, Gangmin, 2015, The phylogenetic affinities of Pellaea connectens, a rare endemic Chinese fern, Phytotaxa 220 (1), pp. 30-42 : 37-39

Argyrochosma connectens (C.Chr.) G.M.Zhang , comb. nov.

Basionym:— Pellaea connectens Christensen (1924: 84) . Type:— CHINA. Sichuan: Jinchuan, on sunny rocks, alt. 21002200 m, 10 October 1922, H. Smith 4800 (holotype S! [S-P-4894]).

Plants found exclusively on rocks ( Fig. 3A–C ). Rhizomes erect, short; scales brown, concolored, subulate-lanceolate ( Fig. 3H ). Fronds densely clustered. Stipe dark brown, 3–8 cm, terete, brittle, with sparse narrow scales at base. Lamina lanceolate to somewhat oblong-triangular, 5–10 × 2–4 cm, 2-pinnate or occasionally 3-pinnate ( Fig. 3E ), papery, glabrous on both surfaces. Ultimate segments discrete, oblong to ovate, 3–6 × 2–3 mm, with lustrous, dark-colored stalks ( Fig. 3F ); segment margins often recurved and forming slightly differentiated pseudoindusia. False indusia pale green, margins irregularly crenate ( Fig. 3 : G). Sporangia submarginal, containing 64 spores per sporangium. Spores brown, tetrahedral-globose, with rugate surfaces ( Fig. 3I ).

Distribution and habitat:— The endemic Chinese species Argyrochosma connectens is known only from Jinchuan (West Sichuan) and Muli county (South-West Sichuan) ( Fig. 4 ). It grows on bare rock crevices along dry-hot valleys at an elevation of 1980–2750 meters, and is adapted to xeric or semi-xeric environments ( Fig. 3A–C ). Its leaves begin to grow in late spring, and wither into dry, black persistent leaves in late autumn. The most common co-existing species is Aleuritopteris niphobola ( Christensen 1924: 88) Ching (1941: 197) and it is occasionally found with some xerophytes, such as A. argentea ( Gmelin 1768: 519) Fée (1852: 154) , Selaginella tamariscina ( Beauvois 1804: 483) Spring (1843: 136) , and Paragymnopteris sargentii ( Christ 1911: 355) Shing (1993: 230) .

Additional specimens examined:— CHINA. Sichuan: Jinchuan (formerly called Hsü Tsing or Suihua ), on sunny rocks, 2100 m, 9 October 1922, H. Smith 4597 ( PE, S) ; 1980 m, 7 October 1957, G. Z. Zhu & X. Li 76619 ( PE) ; on bare rock crevices along the valley of the Dadu River , N 31 ′28″51.88, E 102 ′02″29.83, 2137 m, 18 August 2014, G. M. Zhang 2014090 ( BJFC) . Muli: along the valley of the Tongtian River , 2500 m, September 1959, S. K. Wu s. n. ( KUN, PE) .

Figures

FIGURE 3. Habitat and morphology of Argyrochosma connectens. A–C: habitat; D: plant morphology; E: lamina; F–G: pinna and ultimate segment; H: rhizome scale; I: spore.

FIGURE 4. Distribution of Argyrochosma connectens in China.