tetra (G.) = four, + goni (G.) = angled. Referring the the four-angled culms.
WCM Protologue Reference:
Thunb., Restio: 17 (1788)
Vegetative parts: plants clumped, 0.5–1 m tall, basal diameter 0.4–1 m, crown diameter 0.5–1 m, with rhizomes. Rhizome spreading, unbranched or sparsely branched, culms evenly spaced, 3–10 mm in diam., culms 5–20 mm apart. Fertile culms sparingly branched or branching, square, smooth or finely warty, olivaceous, 0.5–1 m tall, diameter at base 1.5–3.5 mm, diameter at apex 0.6–1.8 mm. Sheaths persistent, with no abscission line, closely convoluted, 15–40 mm long, olivaceous, turning gray, apical margins coriaceous, like the rest of the body or narrowly membranous, hyaline shoulders membranous margins continuing behind awn (but rather narrow), hyaline shoulder 0.01 of sheath body length, apex, excluding the membranous lobes, acute. Sheath-mucro penicellate or awl- or needleshaped, straight and erect, 3–5 mm long, longitudinally striate. Males: male inflorescence with 11–20 spikelets or 21–50 spikelets, paniculate (with the side branches much shorter than the central axis, thus inflorescence has a linear appearance), 15–300 mm long, 10–15 mm wide. Male inflorescence spathes persistent, like the floral bracts, chartaceous or cartilaginous. Male flowers in spikelets. Male spikelets erect on stiff pedicels or sessile, oblong, apex rounded or obtuse, 5–12 mm, 4–6 mm, with 5–10 flowers, pedicels absent ie spikelets sessile or shorter than the spikelets, terete or angular. Male bracts as tall as flowers or taller than flowers, 3.5–4 mm long, ovate, acute or apiculate, cartilaginous, bract upper margin like body of bract, bract awn minute or absent. Male flower 3–3.3 mm long. Male tepals sepals more rigid than petals, cartilaginous, petals chartaceous or membranous, oblong, inner tepals shorter than outer tepals. Male outer lateral tepals conduplicate, glabrous or keel sparsely villous. Anthers 1.5–1.7 mm long, exserted from the flowers. Pistillode present. Females: female inflorescence linear or racemose (Side branches much shorter than main axis), 100–300 mm long, 10–25 mm wide, with 21–50 spikelets or 51–100 spikelets. Female spathes shorter than the spikelets (like the bracts), persistent, coriaceous. Female spikelet pedicel simple or pedicel sparsely branching, oblong, apex rounded, 6–10 mm long, with 3–14 flowers, with 1–3 sterile bracts. Female bracts shorter than flowers or as tall as flowers, 2.5–3.5 mm long, oblong or ovate, acute or apiculate, cartilaginous, apical margin like rest of bract, same as body of bract, awn minute or absent. Female flower 2.8–3.3 mm long, without a fleshy pedicel. Female tepals cartilaginous, glabrous and smooth or keels of lateral sepals sparsely villous, midrib flush with the tepal body, apices acute, inner and outer whorls the same length. Female outer lateral tepals conduplicate, 2.8–3.3 mm long. Female odd outer tepal oblong, 2.7–3.1 mm long. Female inner tepals ovate, 2.2–2.8 mm long. Staminodes present. Styles feathery, white, 3. Style bases free. Ovary with 1 locule, capsules thinwalled, sometimes dropping with seed in (ovary walls papery, easily broken between the carpel margins). Fruit: seed (1.26–)1.38(–1.52) mm long, (0.84–)0.96(–1.04) mm in diameter, shape in side view elliptical, shape in diameter round in cross section, brown, smooth.