Dichanthium* of Clayton
Perennials; leaf-blades flat, sometimes aromatic; ligule membranous. Inflorescence of digitate or subdigitate racemes, sometimes paniculate with a long central axis; racemes with more than 8 sessile spikelets, without homogamous spikelet pairs; internodes and pedicels linear, with a hyaline median line. Sessile spikelet dorsally compressed; callus very short, rounded; lower glume broadly convex to slightly concave on the back, abruptly rounded on the flanks, sometimes with 1-3 circular pits, acute; lower floret reduced to a hyaline lemma; upper lemma often entire, with a glabrous awn. Caryopsis oblong, slightly dorsally compressed. Pedicel¬led spikelet much like the sessile or smaller.
A genus of about 35 species throughout the tropics; 3 species occur in Pakistan.
The boundaries between Bothriochloa, Capillipedium and Dichanthium are somewhat blurred, and DeWet & Harlan (in Am. J. Bot. 53: 94-98. 1966; in Taxon 19: 339-340. 1970; and in Evolution 24: 270-277. 1970) have advocated uniting them. The trouble is largely the result of rapacious hybridisation by a single species; apart from Bothriochloa bladhii and its immediate neighbours, the genera are acceptably distinct both morphologically and genetically.
The essential oils of Bothriochloa, and their taxonomic implications, have been studied by DeWet & Scott (in Bot. Gaz. 126: 207-214.1965) and by DeWet (in Am. J. Bot. 54:384-387. 1967). Heslop-Harrison (in Phytomorph. 11:378-383. 1961) believes that the glume pits play a part in cleistogamous flowering by obstructing the emergence of the anthers.
