Roshevitzia japonica (Thunb.) Tzvelev
Tufted annual or short-lived perennial; culms 10-150 cm high, erect. Leaf-blades flat, up to 30 cm long and 5 mm wide; ligule membranous, 0.3-0.6 mm long, truncate, fimbriate. Panicle linear, 4-50 cm long; branches ascending close to the main axis or spreading and the panicle lanceolate to narrowly ovate or branches contracted in dense remote pseudo-whorls, typically 3-14 cm long, bare towards the base, the spikelets shortly pedicelled and appressed to the secondary branchlets or longer pedicelled and spreading. Spikelets 4-14-flowered, ovate-oblong, 1.3-3 mm long, breaking up from the apex, the rhachilla fragile; glumes narrowly ovate to broadly oblong-elliptic, subequal, 0.4-0.7 mm long, acute to obtuse; lemmas broadly ovate, 0.7-1 mm long, obtuse; anthers 2, 0.2 mm long. Caryopsis ellipsoid, 0.3-0.5 mm long.
Fl. & Fr. Per.: August-October or December.
Type: Japan, herb. Thunberg (UPS).
Distribution: Pakistan (Sind, Baluchistan, Punjab, N.W.F.P. & Kashmir); through-out South and Southeast Asia to tropical and South Africa and Australasia.
An extremely polymorphic species with three main sources of variation;
1. Palea-keels: smooth palea-keels are confined to South and tropical Africa (Eragrostis namaquensis Schrad.)- scaberulous keels are found throughout tropical Africa (Eragrostis diplachnoides) and Asia.
2. Spikelet size: plants with few-flowered spikelets and lemmas less than 1 mm are generally separated as Eragrostis japonica sensu stricto, although similar forms from Africa with smooth palea-keels are called Eragrostis namaquensis, and those with rough keels are called Eragrostis diplachnoides.
3. Panicle-form: three main sorts can be recognised; interrupted with branches in pseudo whorls (Eragrostis koenigii), almost exclusively Asian; partly whorled but more generally open, branches branched from the base (Eragrostis diarrhena, Eragrostis namaquensis and Eragrostis japonica); branches solitary, bare at the base, panicle open (Eragrostis diplachnoides).
Spikelet and lemma size and panicle form are continuously variable with complete intergradation between the extremes; the two sorts of variation work wholly independently of one another. Furthermore the two forms of palea-keel show no correlation with either of the other two variables. In view of this it is quite impracticable to subdivide the Asian species until some Comprehensive biosystematic study has been undertaken. In the meantime, therefore, all Asian species and varieties, however unsatisfactory this may seem, are reduced to synonymy.
Eragrostis japonica belongs to a small group of closely allied species with membranous ligules which have been treated as a separate genus Diandrochloa De Winter. Judgement on this issue has been deferred until variation within the genus as a whole has been more closely studied.
This species is eaten by cattle when other food is not available. It is considered to be a good fodder for buffaloes in parts of India and Pakistan.