Family

Equisetaceae

Nomenclature

Equisetum ramosissimum Desf. subsp. debile (Roxb. ex Vaucher) Hauke, Amer. Fern J. 52: 33. 1962; Laferrière, Fl. Males., Ser. II, Ferns and Fern Allies 3: 287. 1998; Kiew, Fl. Pen. Malaysia, Ser. I, Ferns & Lycoph. 1: 92. 2010. – Equisetum debile Roxb. ex Vaucher, Mém. Soc. Phys. Genève 1: 387. 1822; Tardieu & C.Chr., Fl. Indo-Chine 7(2): 546. 1951; Larsen, Dansk Bot. Ark. 23: 59. 1963; Tagawa & K.Iwats., SouthE. Asian Stud. 5: 32. 1967; Tagawa & K.Iwats., Fl. Thailand 3: 34, f. 1.1–1.3. 1979; Boonkerd & Pollawatn, Pterid. Thailand: 21, 61. 2000; Newman et al., Checkl. Vasc. Pl. Lao PDR: 27. 2007. – Type: Roxburgh s.n., locality unknown.

Description

Fronds monomorphic, to more than 1 m tall; stems with grooves and ridges, the nodes bearing roots, branches, and leaves in whorls; main stems with 8–25 grooves, (0.2–)4–7 mm in diameter, dark towards base, bearing (0–)2–5 branches at the nodes; sheath about 8 mm long, with the teeth up to 7 mm in length, green or brown in the upper portion; teeth pale green to brown, caducous. Cones solitary, terminal on the stems or their branches, about 1 cm long, oblong, cuspidate at apex, subsessile. Sporangiophores hexagonal, peltate, bearing several sporangia ; spores isosporous, mixed with the elators.

Distribution in Thailand

NORTHERN: Chiang Mai, Lampang; NORTH-EASTERN: Loei, Phetchabun; EASTERN: Chaiyaphum; SOUTH-WESTERN: Kanchanaburi; SOUTH-EASTERN: Chanthaburi, Trat.

Distribution in Laos

Hua Phan, Khammouane, Luang Phrabang, Savannakhet.

Wider Distribution

India to S China, Indochina and Taiwan, through Malesia to Polynesia.

Ecology

Terrestrial on wet ground along streams in open areas or in light shade at low to medium altitudes.

Proposed IUCN Conservation Assessment

Least Concern (LC). This species is common and widespread and not under any known threat.

Voucher specimens - Thailand

Middleton et al. 4924, Chiang Mai, Doi Inthanon National Park (E); van Beusekom et al. 4405, Chaiyaphum, Tunkamang (P); Middleton et al. 5131, Loei, Phu Suan Sai (E).

Voucher specimens - Laos

Thorel 2909, Luang Phrabang (P); Vidal 2058, Luang Phrabang (P).