atratus (L.) = clothed in black, + flos (L.) = flower. Referring to the black or dark coloured flowers.
WCM Protologue Reference:
Esterh., Bothalia 15: 420 (1985)
Vegetative parts: plants tufted, 0.4–0.6 m tall, compact, without spreading rhizomes or stolons. Fertile culms unbranched, compressed or compressed after pressing, solid or with a small central cavity, smooth or rugose or finely warty, green or olivaceous, 0.4–0.6 m tall, diameter at base 1–2 mm, diameter at apex 0.9–1.3 mm. Clusters of sterile branches at the nodes of the fertile branches absent. Sheaths more than 1 per culm, persistent, with no abscission line or dropping off, with an abscission line present or sometimes dropping off, abscission present, loosely convoluted, 30–80 mm long, margins entire, dark brown and with a very smooth, almost glossy/shiny surface, upper 1/3 in colour and texture abruptly different from the base, and soon decaying, apical margins broadly chartaceous and soon decaying, hyaline shoulders absent, apex, excluding the membranous lobes, impossible to tell, as the upper portion of the sheaths is absent from herbarium specimens. Sheath-mucro absent. Males: male inflorescence with 21–50 spikelets or 50–100 spikelets or 101–500 spikelets, paniculate, 45–175 mm long, 12–17 mm wide. Male inflorescence spathes caducous, taller than spikelets, chartaceous or cartilaginous (spathes qre quite thin). Male spathellae conspicuous, 6–12 mm long. Male flowers in spikelets. Male spikelets erect on stiff pedicels or sessile, undifferentiated, apex undifferentiated, 2–2.5 mm, 1.7–2 mm, with 3–4 flowers, pedicels as long as the spikelets, terete or angular. Male bracts taller than flowers, 1.8–2.8 mm long, ovate or orbicular, rounded or obtuse or acute, chartaceous or cartilaginous, bract upper margin like body of bract, bract awn less than half as long as the bract body or between half and as long as the bract body. Male flower 1.5–1.7 mm long. Male tepals sepals and petals the same rigidity, cartilaginous, oblong or elliptical or ovate (inner tend to be oblong while outer tepals are ovate or elliptical), inner tepals longer than outer tepals. Male outer lateral tepals conduplicate, glabrous or keel sparsely villous. Anthers 0.6–1 mm long, included in the flowers. Females: female inflorescence linear, 45–180 mm long, 10–17 mm wide, with 11–20 spikelets or 21–50 spikelets or 51–100 spikelets or 101–500 spikelets. Female spathes longer than the spikelets, not obscuring spikelet or obscuring spikelet (partially obscuring), persistent, cartilaginous. Female spathellae conspicuous, 6–13 mm long. Female spikelet pedicel sparsely branching, undifferentiated, apex undifferentiated, 2–3 mm long, with 1–2 flowers, with 0 sterile bracts. Female bracts shorter than flowers, erect, 1.5–3 mm long, oblong or ovate, rounded or acute or acuminate, cartilaginous, apical margin like rest of bract, same as body of bract, awn minute or absent or less than half as long as the bract body. Female flower 2–2.6 mm long, without a fleshy pedicel, six tepals. Female tepals cartilaginous (thin), glabrous and smooth, at least as tall as nut, wrapped around it and obscuring the surface, midrib raised, margins entire, apices rounded or obtuse or acute, inner and outer whorls the same length. Female outer lateral tepals like other tepals, 2–3.2 mm long. Female odd outer tepal oblong or elliptical, 2–3.2 mm long. Female inner tepals oblong or elliptical, 2–3 mm long. Staminodes present. Styles feathery, 3. Style bases free. Ovary with 1 locule, indehiscent. Fruit: indehiscent fruits with a softer ovary wall. Perianth presence on fruits persistent, papery to leathery, not winged. Nut apex smooth, without a distinct cap, wall tuberculate, (1.8–)2.14(–2.48) mm long, (1.2–)1.48(–1.6) mm diam., shape in side view elliptical, shape in top view round in cross section, black. Elaiosome absent.