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FOC | Family List | FOC Vol. 2-3 | Aspleniaceae | Hymenasplenium

16. Hymenasplenium excisum (C. Presl) S. Lindsay, Thai Forest Bull., Bot. 37: 69. 2009.

切边膜叶铁角蕨 qie bian mo ye tie jiao jue

Asplenium excisum C. Presl, Epimel. Bot. 74. 1851; A. resectum Smith var. rahaoense Hayata; A. subresectum Copeland; A. unilaterale Lamarck f. majus C. Christensen; A. unilaterale var. majus (C. Christensen) Sledge; A. unilaterale var. rahaoense (Hayata) Hayata; Hymenasplenium rahaoense (Hayata) H. Itô ex Tuyama; H. unilaterale (Lamarck) Hayata var. rahaoense (Hayata) Nemoto.

Plants 40-60 cm tall. Rhizome long creeping, 3-5 mm in diam., apex scaly; scales blackish brown, narrowly triangular to triangular. Fronds remote, up to 8 mm apart, grayish to dark green when dry, herbaceous, subglabrous; stipe shiny and dark purple to black, 15-32 cm, sparsely scaly to subglabrous; lamina 1-pinnate, narrowly triangular to triangular, 20-40 × 10-18 cm, base truncate and widest, apex acuminate to caudate; rachis shiny, purplish black, subglabrous; pinnae 18-25 pairs, shortly stalked and blackish brown rachis color extending via stipicel onto costa abaxially, trapeziform-oblong to falcate, middle pinnae 5-8(-10) × 1.3-1.8(-2) cm, dimidiate, apex acute, base asymmetrical, acroscopic side truncate and often almost parallel to rachis, basiscopic side of basal pinnae excavate, in middle pinnae narrowly cuneate and entire, acroscopic margin serrate, teeth not retuse; pinnae spreading to ascending. Veins distinct, forking and free, ending below a marginal tooth, basiscopic side with (3 or)4-6 veins lacking. Sori medial, linear, 4-6 mm; indusia persistent, pale brown, semi-elliptic to linear, membranous, entire, opening toward costa.

Shaded wet places in dense forests, on rocks by streams, on tree trunks; 200-1700 m. Guangdong, Guangxi, Guizhou, Hainan, Taiwan, Xizang, Yunnan [Bhutan, India, Indonesia, Malaysia, Myanmar, Nepal, Philippines, Sri Lanka, Thailand, Vietnam; tropical Africa].

Hymenasplenium excisum represents a distinct species complex with sexual diploids (2n = 78) and tetraploids (2n = 156) in China (Yunnan) and Indonesia (Mitui et al., Amer. J. Bot. 76: 1691. 1989; Cheng and Murakami, J. Plant Res. 111: 496. 1998). Cheng and Murakami (loc. cit.) mentioned a new endemic species complex, "H. costarisorum," from two localities in S Yunnan, said to be similar to H. excisum in gross morphology but different in smaller size, larger number of pinnae, more strongly reflexed lower pinnae, and sori restricted to the distal part of the pinnae. This undescribed taxon containing two cytotypes, a sexual diploid (n = 36) and a sexual tetraploid (n = 72), has a basic chromosome number of x = 36, which is universal in Aspleniaceae, except Hymenasplenium (with x = 38 and x = 39). Molecular data (Murakami, J. Plant Res. 108: 257-268. 1995) showed that this "species" is closely related to H. obscurum (with a chromosome number of x = 39).

"Asplenium rahaoense" (Y. Yabe ex Matsumura & Hayata, J. Coll. Sci. Imp. Univ. Tokyo 22: 605. 1906) belongs here but is a nomen nudum and was not therefore validly published (Melbourne Code, Art. 38.1(a)).


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