Reed-like herbs along margins or river or swamps, with creeping underground stems, aerial stems erect, sometimes with branching at the nodes, sometimes with a whorl of smaller branches, longitudinally grooved, articulate, with a sheath at each node, the internodes green and rough to the touch, hollow, leaves reduced to a single whole of minute, +/- deciduous teeth on the rim of the sheath at each node. Sporangia borne on the backs of stalked, peltate sporangiophores, arranged in a compact terminal cone; spores rounded, green, with 4 coiled bands.
Basically a northern hemisphere family of a single genus with c. 24 species. Equisetum debile is the sole species in Papuasia.
Terrestrials or subaquatics of steam banks, often immersed for considerable periods, of moderate size. Rhizome creeping underground bearing roots at the nodes; aerial stems erect, terete, longitudinally grooved, stomata in the grooves, siliceous cells on the ridges, jointed, hollow with a large central hollow (centrum) surrounded by small vallecular canals beneath each groove, and smaller carinal canals beneath each ridge, photosynthetic, the leaves reduced to persistent or deciduous scariose teeth in a single whorl on an entire sheath at each node, the stem unbranched or with 1 - many branches borne in a whorl beneath the nodal sheath; vascular bundles of a region of phloem flanked by 2 patches of xylem immediately outside each carinal canal, uniting to form a complete cylinder (a medullated protostele) at the nodes. Sporangia borne in groups of 5-10 on the underside of peltate, +/- hexagonal sporangiophores, aggregated into a compact ovoid or ellipsoid terminal strobilis. Spores round, green , with 4 coiled, elongate-spathulate bands (elaters) with a common point of attachment, that uncoil and recoil with changes in humidity.
Distribution: An almost cosmopolitan genus of 23 species, noticeably absent from Australia and New Zealand, with a single species in Papuasia:
Croft, J.R. 1985. Ferns and Fern Allies, in Leach, G.J. & Osborne, P.L. 1985. Freshwater Plants of Papua New Guinea. 33 - 74, f. 6 - 13, pl. 5 - 7.
Hauke, R.A. 1961 - 1962. A taxonomic reorganization of Equisetum, subgenus Hippochaete, I - IV. Amer. Fern J. 51: 131 - 137; 52: 29 - 35, 57 - 63, 123 - 130.
Hauke, R.A. 1963. A taxonomic monograph of the genus Equisetum subgenus Hippochaete. Bieh. Nova Hedwigia B: 1 - 123.
Page, C.N. 1972. An assessment of inter-specific relationships in Equisetum. New Phyto.. 71: 355 - 369, f. 1 - 2, pl. 1 - 4.
Reed, C.F. 1971. Index to Equisetophyta. Reed Herbarium, Baltimore, U.S.A.
Schaffner, J.N. 1925. Main lines of evolution in Equisetum. Amer. Fern J. 15: 8; 15: 35.
Schaffner, J.N. 1930. Diagnostic analysis and phylogenetic relationships of the main groups of Equisetum. Amer. Fern J. 20: 11.
Schaffner, J.N. 1930b. Geographic distribution of the species of Equisetum in relation to their phylogeny. Amer. Fern J. 20: 89 - 106.
A single river-side species in Papuasia:
Synonyms: Equisetum ramosissimum Desf. subsp. debile (Roxb.) Hauke; Hippochaete ramosissima (Desf.) Borner subsp. debilis (Roxb ex Vauch.) Love & Love; Equisetum diffusum auct. non D.Don: F. Muell. 1975.
Stems 30 -100 cm or more tall, arising from a dark brown, segmented rhizome with nodes c. 1 cm apart, aerial segments 1 - 10 cm long, 2 - 5 mm diameter, inserted in a cup 3 - 10 mm deep at the end of the next lower segment, pale to mid green, longitudinally striate, very finely scabrid along the ridges, the striae ending in scariose or dark traingular teeth to 1 mm long; stems near the water generally unbranched, those away from the water often with 1 -6 radial branches arising from the base of the apical cup of each segment, the branches sometimes only a few segments long and all fertile. Cones terminal on the main branch or on side branches, c. 10 -15 mm long, 5 - 7 mm across, back when mature, yellow or pale orange internally, sporangiophores radially arranged in up to 12 rows; spores minute, bright green.
Habitat: Beside streams, still water bodies, in swamps, beside road cuttings, in full sun or partial shade, from sea level to 3600 m altitude.
Distribution: A widely distributed species from Africa, Asia, Japan, southwards through the Philippines, Indonesia, the New guinea mainland, The Bismarck Archipelago, the Solomon Islands eastwards to New Caledonia and Fiji. Does not occur naturally in Australia and New Zealand.
Notes: The altitudinal range of this species is most surprising. Covering the entire range from humid lowlands to severe alpine conditions, it has the greatest tolerance in Papuasia and is rivaled by very few, if any, other plants.
The stems of Equisetum accumulate crystals of silica, a strong abrasive, and European species have been given the name "scouring rush". In traditional times in New Guinea, Equisetum was used to polish ornaments and to smooth handles etc.; these days it is still used, in cleaning aluminium cooking pots.