These are leafy annual grasses. The inflorescence is a narrow pyramidal raceme of slender, spreading or deflexed spikes. Spikelets are small, biseriate and crowded on one side of the spike and not jointed at the base; rachilla is slender, jointed and produced beyond the flowering glumes and bearing an imperfect glume. There are four to five glumes. The first two glumes are the longest, lanceolate, 1-nerved, keeled and awned. The second glume is slightly longer than the first. The third and the fourth glumes are very small, hyaline, broadly ovate, 1-nerved. Lodicules are present. Stamens are three and anthers didymous and small. Grain is narrowly ovoid and trigonous. [Illustration: Fig. 210.--Dinebra arabica. 1. Full plant; 2. leaf showing the ligule.] =Dinebra arabica, _Jacq._= This grass is an annual with stems erect or with a geniculate base, tufted, slender or stout; some of the lower nodes of the geniculate part of the stems bear roots; the internodes are green or purple tinged and glabrous. The _leaf-sheath_ is thin, somewhat loose, usually glabrous, rarely sparsely hairy. The _ligule_ is a short membrane irregularly cut at the top. The _nodes_ are glabrous. The _leaf-blade_ is linear, very finely acuminate, rough on both the surfaces, thinly and very sparsely hairy; the base of the blade is contracted and purple tinged towards the margin, midrib is prominent with three or four main veins on each side; the margins are very finely, closely serrate. [Illustration: Fig. 211.--Dinebra arabica. 1 and 2. The front and back view of a portion of a spike; 3. spikelet; 4, 5 and 6. the first, second and third glumes; 7. palea of the third glume; 8. lodicules, ovary and stamens.] The _inflorescence_ is a long erect narrow pyramidal panicle varying in length from 2 to 16 inches; the lower branches sometimes bear several spikes and attain 6 inches in length; the _peduncles_ are short or long, purple tinged and the main _rachis_ is smooth except at the top, angular and grooved. The _spikes_ are numerous, greenish or purple tinged, slender, erect or spreading or sometimes deflexed, opposite, alternate or in fascicles of two to four varying in length from 1/4 to 2-1/2 inches; the _rachis_ of the spike is trigonous, flattened out ventrally and with a ridge on the ventral side and the margins are scabrid. The _spikelets_ are few to many in a spike, alternate, closely imbricating, sessile, about 1/6 inch long including the awns, usually three flowered, rarely less or four flowered; the _rachilla_ is very slender, jointed at the base, produced and jointed between the flowering glumes.