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

2. Hymenasplenium cheilosorum (Kunze ex Mettenius) Tagawa, Acta Phytotax. Geobot. 7: 84. 1938.

齿果膜叶铁角蕨 chi guo mo ye tie jiao jue

Asplenium cheilosorum Kunze ex Mettenius, Abh. Senckenberg. Naturf. Ges. 3: 177. 1859; A. heterocarpum Wallich ex Hooker (1859), not Blume (1828).

Plants 25-60 cm tall. Rhizome long creeping, 2.5-4 mm in diam., apex scaly; scales narrowly triangular to triangular, entire or sparsely fimbriate at base. Fronds up to ca. 5 mm apart, dark green when dry, membranous-herbaceous, subglabrous; stipe grayish black to dark purplish, shiny, 10-20 cm, base with scales similar to those on rhizome; lamina 1-pinnate, narrowly oblong-triangular, 15-35 × 3-5(-7) cm, truncate at base, acuminate-caudate at apex; rachis shiny, dark purplish; pinnae 25-40 pairs, almost sessile, rectangular to trapeziform or lunate, 1.8-2.5(-3.6) × 0.5-0.9 cm, dimidiate, apex obtuse, base asymmetrical, acroscopic side truncate to cuneate and parallel to rachis, basiscopic side cut away and narrowly cuneate and entire, acroscopic margin deeply crenate to dentate with lobes (ca. 1 mm wide) cut up to 1/4-2/5 of way to costa, lower pinnae spreading or deflexed, upper pinnae ascending. Veins distinct, forking and free, 1 vein per marginal lobe and ending below sharp tooth, basiscopic side with 6 or 7 veins lacking. Sori linear, 1-3 mm, at tip of subtending veins and located in marginal teeth; indusia persistent, yellowish brown to deep brown, semi-elliptic, membranous, entire. Plants sexual diploids (2n = 78), agamosporous triploids with "n" = 2n = 117, or tetraploids (2n = 156).

In soil or on wet rocks along streams in forests; 500-1800 m. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Taiwan, Xizang, Yunnan, Zhejiang [Bhutan, India, Indonesia, Japan, Malaysia, Myanmar, Nepal, Philippines, Sri Lanka, Thailand, Vietnam].

As presently circumscribed, Hymenasplenium cheilosorum is an aggregate of a widespread triploid agamosporous taxon and probably more local (Yunnan) sexual (diploid) and tetraploid (Guizhou) taxa. This distinctive complex was examined cytologically by Mehra and Bir (Cytologia 25: 17-27. 1960) using Himalayan material and later again by Mitui et al. (Amer. J. Bot. 76: 1689-1697. 1989) using Japanese plants. Mehra and Bir (loc. cit.) listed E Himalayan H. cheilosorum as a triploid agamosporous plant but with the incorrect chromosome number of "n" = 108 (based on x = 36). Mitui et al. (loc. cit.: 1690-1691) showed that both Himalayan and Japanese H. cheilosorum are apomictic and triploid, but with "n" = 2n = 117 (based on x = 39) chromosomes. Cheng and Murakami (J. Plant Res. 111: 495-500. 1998) found an ancestral sexual diploid taxon in Yunnan, with spore mother cells showing 39 bivalents at metaphase I, but without describing it formally as a separate species. We found a single tetraploid population in Guizhou (Yaoren Shan). Species of this alliance can be distinguished from the closely related, also sexually reproducing, H. inthanonense N. Murakami & J. Yokoyama from N Thailand, by their more terminal sori and more dimidiate pinnae.


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