2. Cyperus, Linn.

Annual or more commonly perennial herbs. Stems erect, simple below the inflorescence. Leaves at the base of the stem, usually long, the lowest sometimes reduced to sheaths. Inflorescence umbellate or capitate, often large and compound; bracts at the base long, leaf-like, spreading. Spikelets oblong or linear, compressed; rhachilla persistent. Glumes usually many, distichous; the two lowest empty; four at least and generally many of the succeeding ones hermaphrodite and fruit-bearing, falling away from the rhachilla one by one, commencing with the lowest; the uppermost 1–3 sterile or empty. Stamens 2–3, rarely 1. Style continuous with the ovary, not thickened at the base; branches 3, filiform. Nut triquetrous or plano-convex, the flat face against the rhachilla, surface smooth.

A large genus of over 300 species, most abundant in the tropical and subtropical districts of both hemispheres, comparatively rare in temperate regions. The two New Zealand species are widely distributed; one of them is certainly a recent introduction, and possibly the other as well.

Small, 1–3 in. high. Inflorescence of a single head; spikelets 1–3	1. C. tenellus.
Tall, 1–2 ft. high. Inflorescence in a compound umbel; spikelets very numerous	2. C. vegetus.

The tropical C. rotundus, Linn., easily recognised by the black ovoid tubers on the creeping stolons, and hence frequently known by the name of "nut-grass," has become naturalised in the vicinity of Auckland. It is a most pernicious weed.