equisetum = horsetails. Referring to the similarity in the vegetative growth-form between this species and the genus Equisetum.
WCM Protologue Reference:
(Mast.) Mast., J. Linn. Soc., Bot. 21: 583 (1885)
Vegetative parts: plants tufted, 1–2 m tall, basal diameter 0.05–0.3 m, crown diameter 0.3–0.7 m, compact, without spreading rhizomes or stolons. Fertile culms unbranched or branching or branches whorled at each node (old plants tend not to have the whorled branches typical of younger plants), round (not compressed), solid or with a small central cavity, smooth or finely rugulose, olivaceous, 0.5–1.5 m tall, diameter at base 1.7–4.5 mm, diameter at apex 1–2 mm. Clusters of sterile branches at the nodes of the fertile branches present (often present, but sometimes fertile branches are simple) or absent. Sterile branches present while flowering or present post flowering. Sheaths more than 1 per culm, dropping off, with an abscission line present, loosely convoluted, 20–50 mm long, margins entire, reddish-brown with a few tan speckles, lower two-thirds of sheath darker in colour than upper third, upper 1/3 in colour and texture abruptly different from the base, and soon decaying, apical margins narrowly membranous, hyaline shoulders absent, apex, excluding the membranous lobes, obtuse. Sheath-mucro penicellate, straight and erect, 2–3 mm long. Sterile branch leaf-sheath 1.5–2.5 mm long (these sheaths are generally quite small but otherwise similar to the larger sheaths). Males: male inflorescence with 50–100 spikelets or 101–500 spikelets or 501 and more spikelets, paniculate, 50–190 mm long, 15–30 mm wide. Male inflorescence spathes caducous, taller than spikelets, cartilaginous. Male spathellae conspicuous, 5–15 mm long. Male flowers in spikelets. Male spikelets erect on stiff pedicels or sessile, undifferentiated, apex undifferentiated, 2.5–3 mm, 2–3.5 mm, with 3–7 flowers, pedicels shorter than the spikelets or as long as the spikelets, terete or angular. Male bracts shorter than flowers, 0.8–1 mm long, orbicular (they have a rather 'undifferentiated' shape as they are wrapped around the base of the flowers and the margins are uneven), rounded, cartilaginous, bract upper margin membranous, thinner texture than the body, bract awn minute or absent. Male flower 1.5–2.5 mm long. Male tepals sepals and petals the same rigidity, cartilaginous, ovate, inner tepals longer than outer tepals. Male outer lateral tepals keeled or winged or as other tepals, glabrous. Anthers 1–1.3 mm long, included in the flowers. Females: female inflorescence interrupted or linear, 50–200 mm long, 10–20 mm wide, with 6–10 spikelets or 11–20 spikelets or 21–50 spikelets. Female spathes longer than the spikelets, obscuring spikelet, persistent, cartilaginous (quite sturdy). Female spathellae conspicuous, 5–15 mm long (the female spathellae are usually much wider than the male spathellae). Female spikelet pedicel simple, undifferentiated, apex undifferentiated, 3–5 mm long, with 5–10 flowers, with 0 sterile bracts. Female bracts shorter than flowers, erect, 0.5–1.5 mm long, ovate or orbicular (the shape and apex of the bracts is variable. The ovate bracts are elongated - thus 'lanceolate' in shape), obtuse or acute, cartilaginous, apical margin like rest of bract, same as body of bract, awn minute or absent. Female flower 1.8–2.5 mm long, without a fleshy pedicel, six tepals. Female tepals cartilaginous, glabrous and smooth, at least as tall as nut, wrapped around it and obscuring the surface, midrib raised, margins entire, apices rounded, inner and outer whorls the same length. Female outer lateral tepals like other tepals or conduplicate (the flowers are at times somewhat laterally compressed so that the outer lateral tepals do appear to be keeled), 1.8–2.3 mm long. Female odd outer tepal oblong, 1.7–2.3 mm long. Female inner tepals oblong, 1.7–2.3 mm long. Staminodes present. Styles 3. Style bases free. Ovary with 1 locule, indehiscent. Fruit: indehiscent fruits with a softer ovary wall. Nut apex smooth, without a distinct cap, wall smooth or wall tuberculate, (2–)2.16(–2.44) mm long, (0.96–)1.1(–1.32) mm diam., shape in side view elliptical, shape in top view round in cross section, brown. Elaiosome absent.