Rhynchospora barrosiana Guagl.

Perennial herb 0.3-1.0 m in height, tufted. Rhizome merely linking shoots of tuft. Culms erect, 2-6 noded, trigonous to sharply triangular, the faces flat or concave, margins usually smooth, 1.25-1.5 mm wide (at half length). Radical leaves several to numerous, often spreading, sheaths splitting early, persistent but not forming dark closely enveloping bases to shoots; blades 70-500 mm long, 1.0-3.5 mm wide, usually expanded, channelled above, midrib projecting below, tapering gradually to a triangular or flat apex, glabrous, margins smooth or minutely scabrid. Cauline leaves several, gradually reduced upwards, sheath entire, mouth truncate to broadly U-shaped, generally dark coloured, blade as for radical leaves. Inflorescence compound, usually a terminal cymose head, or 2 or 3 smaller units closely packed forming a pseudo-head, usually wider than long (deep), shortly extended from 1 or more apical culm nodes and leaf sheaths, sometimes accompanied by 1 or 2 heads, or pseudo-heads, from 1 or 2 nodes below; each cymose head of (20-)30-50(-80) closely packed spikelets all held at approximately the same level. Bracts blade(s) of uppermost 1-3 cauline leaves, overreaching or laterally accompanying the terminal head, appearing as fairly conspicuous ‘bracts’, leaf-like but reduced. Spikelets 4.5-5.3(-8.0) mm long, (1.6-)2.2-2.5 mm wide, lanceolate to oval, acute, maturing 1-5 achenes, dark brown at maturity. Glumes numerous, lowest 3-5 sterile, increasing upwards to fertile, 2.7-3.2 mm long (including mucro up to 0.6 mm), midrib projecting, lateral faces appearing nerveless, apex acute to mucronate, all glumes disarticulating early and sequentially from straight rhachilla, abscission scars clear. Hypogynous bristles outside stamens, 3-6(-7) uniform or variable in length within a floret (typically 3 + 3, shorter than, equalling or slightly exceeding achene alone) developed from persistent ‘pedicel’ 0.2-0.3 mm long. Stamens (3-)2(-1); filaments 1.5-2.8 mm long after anthesis. Achene 1.45-1.8 mm long (excluding style base, including ‘pedicel’), 1.05-1.25 mm wide, elliptic to obovoid, biconvex, yellow-brown to chestnut-brown; surface transversely rugose (ridges projecting, about 12 across face of achene). Style deeply bifid; base 0.4-0.8 mm long, 0.7-0.9 mm in breadth across attachment to achene, deltoid in outline.