Diplachne Beauv., Syn. Pl. Glumac. 1: 287. 1854.

Snow, Neil, Peterson, Paul M., Romaschenko, Konstantin & Simon, Bryan K., 2018, Monograph of Diplachne (Poaceae, Chloridoideae, Cynodonteae), PhytoKeys 93, pp. 1-102 : 10-11

Diplachne Beauv., Syn. Pl. Glumac. 1: 287. 1854.

Diplachne P. Beauv., Ess. Agrostogr. 80. 1812. Leptochloa subg. Diplachne (P. Beauv.) A. Gray, Man., rev. ed., 555. 1857. Diplachne P. Beauv. sect. Eudiplachne Asch. and Graebn., Syn. Mitteleur. Fl., 2: 339. 1900. Type: Diplachne fascicularis (Lam.). P. Beauv. [= Diplachne fusca subsp. fascicularis (Lam.) P.M. Peterson & N. Snow].

Type species.

Diplachne fusca

Description.

Plants cespitose, annual or perennial, arising from fibrous roots or sometimes rhizomatous. Culms (3-)10-250(-300) cm tall, round or somewhat compressed, mostly ascending to erect, often geniculate at lower nodes (rarely decumbent and rooting at nodes; sometimes highly reduced and prostrate), often branching. Internodes hollow or with stellate arenchyma; nodes glabrous. Leaves cauline, midrib ( “keel”) prominent proximally on upper surface, blades flat or becoming involute when dry, apex attenuate; sheaths open, longer or shorter than internodes. Ligules (1.5-)4-8(-15) mm, membranous or hyaline, acute to attenutate but becoming lacerate in age. Inflorescence a panicle of spicate primary branches, terminal or sometimes lateral, completely exserted or partially enclosed basally in sheath. Panicle branches numerous, steeply erect to divergent or even reflexed (in age) but mostly ascending, stiff, minutely scabrous, whorled, subwhorled or (mostly) alternate along the rachis, typically one-sided throughout their length with spikelets in 2 rows, each branch terminating in a functional spikelet. Spikelets rounded to somewhat compressed, becoming more rounded or flattened in maturity (with caryopsis), distant to tightly imbricate, green to plumbeous (lead-coloured) in flower; callous glabrous; florets mostly (2-)4-12(-20), perfect (occasionally male or female); rachilla only rarely prolonged. Glumes unequal, membranous, 1-nerved. Lemmas 3-nerved, glabrous to serious on midvein and lateral nerves, especially proximally; apex acute, obtuse, sometimes emarginate, awnless, mucronate or awned; lateral nerves distinct and occasionally excurrent. Palea membranous, typically subequal to lemma. Stamens 1, 2, or (mostly) 3, anthers 0.2-2.7 mm long, yellow or maroon. Caryopsis elliptic to narrowly elliptic in hilar profile; dorsally compressed. n =10; 2 n =19, 20.

Vernacular name.

Given unstable generic boundaries, no common name has been applied consistently. For English, “diplachne” is simply recommended given its shortness and ease of pronunciation.

Key to the species of Diplachne

1	Plants erect or geniculate, to 170 cm tall, sometimes rooting at the lower nodes; culms hollow; lemmas more or less hairy on the nerves; sheaths glabrous; panicle branches 3-25 cm long, relatively stiff, mostly erect to ascending, much less frequently divergent to reflexed; florets sometimes tightly imbricate entirely or mostly concealing the rachilla	Diplachne fusca
-	Plants mostly erect, to 300 cm tall, sometimes rhizomatous; culms with abundant stellate aerenchyma; lemmas glabrous or with short hairs near the base of the nerves; lower sheaths pubescent, but becoming glabrous with age; panicle branches 12-18 cm long, somewhat lax, probably divergent to reflexed when fresh (not confirmed in field); florets less tightly imbricate and sometimes revealing rachilla	Diplachne gigantea