The inflorescences are spike-like racemes, consisting of involucellate clusters of shortly pedicelled spikelets jointed on a simple rachis. The involucel consists of hardened spike-like bristles connate at the base into a short coriaceous cup, which is surrounded by erect or squarrose bristles. Spikelets one to three in each involucel, persistent, 1- to 2-flowered, with three or four glumes. The first glume is very small or absent. The second and the third glumes are subequal 5- to 7-nerved. The third glume is longer than the second with male flower or not, paleate. The fourth glume is coriaceous, with a bisexual or female flower. Lodicules are two. Stamens are three. Styles are long, free or connate below. Grain is broad, oblong and compressed.
KEY TO THE SPECIES
- Base of involucel rounded; inner bristles shorter, erect, not ciliateand connate at base. 1. C. biflorus.
- Base of involucel turbinate, inner bristles longer, spreading and spinescent, ciliate at base 2. C. catharticus.
Cenchrus biflorus, Roxb.
This is an annual with erect simple stems, 6 to 24 inches long.
The leaf-sheath is glabrous or nearly so, with hairs at the mouth.
The leaf-blade is linear-lanceolate, finely acuminate, glabrous or hairy, 3 to 10 inches long and 1/8 to 3/8 inch broad.
The inflorescence is a solitary cylindric raceme of involucels, 2 to 4 inches long, enclosed in the uppermost leaf-sheath; the rachis is flexuous, angular and smooth. Involucels usually with two, rarely three spikelets, loosely imbricate, rounded at the base; the inner bristles are erect, dorsally flat, subulate-lanceolate, puberulous and with thickened margins, about 1/8 inch long. The outer are shorter than the inner, glabrous, erect or subsquarrose and as long as the sessile spikelets.
The spikelets are about 1/6 inch long, sub-globose, with four glumes. The first glume is about 1/10 inch long, ovate-acuminate, very thin, hyaline, nerveless or rarely 1-nerved. The second glume is broadly ovate, 1/6 inch long, hyaline, acute, 1-nerved. The third glume is slightly longer than the second, oblong-ovate, apiculate, 5-nerved and paleate; palea 1/8 inch obtuse. The fourth glume is as long as the third, ovate, obtuse, paleate. Anthers are three. Styles free almost to the base. The grain is 1/12 by 1/16 inch orbicular oblong, compressed, smooth and pale brown.