pachys (G.) = thick, stout, + stachys (G.) = spike. Referring to the almost round spikelets.
WCM Protologue Reference:
Kunth, Enum. Pl. 3: 399 (1841)
Vegetative parts: plants tufted, 0.5–1 m tall, basal diameter 0.1–0.2 m, crown diameter 0.5–1 m, compact, without spreading rhizomes or stolons. Fertile culms sparingly branched, smooth, olivaceous, 0.5–1 m tall, diameter at base 1–2 mm, diameter at apex 0.5–1.5 mm. Sheaths closely convoluted, 10–30 mm long, brown, upper 1/3 in colour and texture abruptly different from the base, and soon decaying, apical margins narrowly membranous, hyaline shoulders tall, acute, hyaline shoulder 0.2–0.4 of sheath body length, apex, excluding the membranous lobes, acuminate. Sheath-mucro penicellate, straight and erect, 2–6 mm long, upper portion of the sheaths weak and soon decaying, leaving an acute to acuminate relict. Males: male inflorescence with 2–5 spikelets or 6–10 spikelets, racemose or paniculate, 30–75 mm long, 12–18 mm wide. Male inflorescence spathes persistent, like the floral bracts, coriaceous. Male flowers in spikelets. Male spikelets erect on stiff pedicels or sessile, elliptical or ovate, apex rounded, 12–20 mm, 6–8 mm, with 20–30 flowers, pedicels absent ie spikelets sessile or shorter than the spikelets, terete or angular. Male bracts shorter than flowers or as tall as flowers, 5–6 mm long, square, acuminate, cartilaginous, bract upper margin with honeycombed cells, which eventually decay, bract awn minute or absent or less than half as long as the bract body, apices dark to black. Male flower 4–5 mm long. Male tepals sepals more rigid than petals, cartilaginous, petals membranous, oblong, inner tepals shorter than outer tepals or inner and outer tepals the same length. Male outer lateral tepals conduplicate, keel densely villous. Anthers 2–2.3 mm long, exserted from the flowers. Pistillode present. Females: female inflorescence racemose, 16–60 mm long, 15–25 mm wide, with 1 spikelet or 2–5 spikelets. Female spathes insignificant, persistent, coriaceous. Female spikelet sessile, elliptical, apex rounded or acute, 18–25 mm long, with 5–10 flowers, with 2–6 sterile bracts. Female bracts taller than flowers, 10–15 mm long, square, acuminate, cartilaginous, apical margin with honeycombed cells, darker than body of bract, awn minute or absent or less than half as long as the bract body. Female flower 7–8.5 mm long, without a fleshy pedicel. Female tepals cartilaginous, keels of lateral sepals densely villous, midrib flush with the tepal body, apices acute, inner and outer whorls the same length. Female outer lateral tepals conduplicate, hidden by bracts, or bracts are shorter than flowers or exserted past bracts, 7–8.5 mm long. Female odd outer tepal oblong, 7–8 mm long. Female inner tepals oblong or ovate, 6–7 mm long. Staminodes present. Styles feathery, 3. Style bases free. Ovary with 2 locules, dehiscent. Fruit: seed 2.1–2.4 mm long, 1.2–1.8 mm in diameter, shape in side view elliptical or oblong, shape in diameter triangular in cross section, silvery or brown, colliculate.