Flora of New Zealand Series

Isolepis cernua (Vahl) Roem. et Schult. Syst. Veg.  2,  1817,  106.

Type locality: Portuguese. Almost cosmopolitan, occurring in all temperate and tropical countries except S.E. Asia.

Variable in size, in dense tufts or with a shortly branched ascending rhizome. Culms (2)–6–12–(20) cm. long, us. c. 0.5 mm. diam. or less, but occ. up to 1 mm. diam. Lvs 1–4 or 0, ± = culms, or much < culms, c. 0.5 mm. wide, or often reduced to shortly mucronate sheaths; sheaths dark red-purple at the base, lighter brown towards the truncate orifice. Infl. of 1–(2–3) spikelets; subtending bract ± = or us. slightly > spikelets, 0.3–0.7–(2.5) cm. long, setaceous or lf-like, caducous. Spikelets 2–5 × (1)–1.5–2.5 mm., elliptical, obtuse, almost white, or green, or with red-brown markings. Glumes 1–2 mm. long, broadly ovate, only slightly concave with keel not prominent, obtuse, green to very pale straw coloured, or with red-brown markings at the sides, margins entire, membr., rounded towards the tip, or with the keel at tip of glume somewhat thickened and ± excurrent, lateral nerves conspicuous. Hypog. bristles 0. Stamens 3, rarely 2 or 1 in occasional glumes. Style-branches 3. Nut us. slightly < 1 mm. long, but occ. slightly > 1 mm., c. 0.5 mm. wide, obovoid or occ. elliptical-obovoid, plano-convex, or subtrigonous and obtusely angled at the back, rounded at the tip and sharply apiculate, red-brown or dark grey at maturity, minutely but very distinctly reticulate.

DIST.: N., S., St., Ch., Sn., Ant., A., C.

Coastal throughout, in damp sand hollows and on rock.

There is considerable variation within S. cernuus in N.Z. in size of plant and in colour of glumes. Towards the southern half of the South Id and in the outlying islands plants are stouter and more rigid, the bract subtending the infl. is longer, and the glumes are more often tinged with red-brown and sometimes shining, with the keel enlarged towards the tip of the glume. Most specimens from the Snares Is have culms above average length, while specimens from Auckland Is (e.g. CHR 157235) and Campbell Id (e.g. CHR 117954, 117959) are very robust, though of average height, and have conspicuous dark red-brown colouring on the glumes.