Hymenasplenium inthanonense N.Murak. & J.Yokoy.




Hymenasplenium inthanonense N.Murak. & J.Yokoy., Thai Forest Bull., Bot. 26: 43. 1998; Boonkerd & Pollawatn, Pterid. Thailand: 179. 2000.


Rhizome long creeping, 3–6.5 mm diam., bearing two rows of alternate fronds closely (2–5 mm apart) on dorsal surface, scaly near apex; scales dark in colour, gradually narrowing towards apex, up to 5.5 by 1 mm, clathrate, the cell walls very thick. Stipes 15–22 cm long, dark purple, polished but dirty on the lower portion bearing scales. Rachis similar colour to stipe, glabrous, grooved above. frond 30–40 cm long, 4–7 cm wide, pinnate, narrowly lanceolate in outline, subtruncate at base, attenuately acuminate at apex; pinnae 2–3 cm long, 0.7–1.1 cm wide, 30–40 pairs, subquadrangular, dimidiate, the lower half very narrow, the midrib close to entire lower margin, rounded at apex, truncate at acroscopic base, lobed to 1/7–1/5 way on upper margin, lobes rounded or forked at apex, 1.5–2 mm broad, lower pinnae shortly stalked, thin, pale green; veins all free, distinct and slightly raised on both surfaces, the lateral veins once forked, the two branches passing to each tooth of a lobe. Sori supramedial, not confined to lobes, 2–4 mm long; indusia thin, opening outwardly. Reproduction sexual, with 64 spores per sporangium .

Distribution in Thailand

NORTHERN: Chiang Mai.

Wider Distribution

Endemic to Thailand.


Terrestrial or lithophytic fern on muddy banks at high altitude >2000 m.

Proposed IUCN Conservation Assessment

Vulnerable B2ab(iii,v). Although the number of locations are not entirely clear it is likely to be less than 10 as the species only grows in one valley on Doi Inthanon. The authors of the name note that although these plants are in the National Park that in 1994 alone there was serious damage due to erosion and fire in several of the populations.

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