Acrachne racemosa

HABIT Annual; caespitose. Basal innovations intravaginal. Culms geniculately ascending, or decumbent; 15–75 cm long; 1–3 mm diam.; 2–5 -noded. Lateral branches sparse. Leaves cauline. Leaf-sheaths as wide as blade at the collar; keeled. Ligule a ciliolate membrane; 0.5–1.25 mm long. Leaf-blades 15–75 cm long; 5–11.5 mm wide. Leaf-blade surface smooth; glabrous, or pilose; sparsely hairy. Leaf-blade margins cartilaginous. Leaf-blade apex attenuate; filiform.

INFLORESCENCE Inflorescence composed of racemes.

Racemes 3–25; digitate, or borne along a central axis; in several whorls; unilateral; 1.5–10 cm long. Central inflorescence axis 0–15 cm long. Rhachis angular; terminating in a sterile spikelet. Spikelet packing broadside to rhachis; regular; 2 -rowed.

Spikelets appressed; solitary, or in pairs. Fertile spikelets sessile; 1–2 in the cluster.

STERILE SPIKELETS Apical sterile spikelets rudimentary; 1 in number.

FERTILE SPIKELETS Spikelets comprising 6–25 fertile florets; with diminished florets at the apex. Spikelets oblong; laterally compressed; 5.5–13 mm long; 2.5–3 mm wide; breaking up at maturity; rhachilla persistent; retaining paleas; tough throughout, or fragile above; with the distal florets falling as a whole. Rhachilla internodes 0.1 mm long; eventually visible between lemmas.

GLUMES Glumes deciduous; similar; shorter than spikelet. Lower glume lanceolate; 1.2–2.9 mm long; 0.5–0.8 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume lateral veins absent. Lower glume apex acuminate; mucronate. Upper glume ovate; 1.5–3 mm long; 0.5–0.7 length of adjacent fertile lemma; membranous; 1-keeled; 1 -veined. Upper glume primary vein scabrous. Upper glume lateral veins absent. Upper glume apex entire; acuminate; mucronate.

FLORETS Fertile florets recurved at tip. Fertile lemma ovate; laterally compressed; ovate in profile; 2.1–2.8 mm long; membranous; yellow to mid-green; keeled; 3 -veined. Lemma midvein scaberulous. Lemma lateral veins excurrent. Lemma apex entire; acute; awned; 1 -awned. Principal lemma awn 0.3–0.9 mm long overall. Palea ovate; bowed outwards; 0.8 length of lemma; 2 -veined. Palea keels scabrous. Palea apex dentate; 2 -fid; acute. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; cuneate; fleshy. Anthers 3; 0.4 mm long. Stigmas 2; protandrous; laterally exserted.

FRUIT Caryopsis with free soft pericarp; ellipsoid; isodiametric; biconvex; estipitate; sulcate on hilar side; 0.8–1 mm long; rugose; apex unappendaged. Embryo 0.4 length of caryopsis. Hilum punctiform. Endosperm farinose. Disseminule comprising a caryopsis.

DISTRIBUTION Africa: north, Macaronesia, west tropical, west-central tropical, northeast tropical, east tropical, southern tropical, and south. Asia-temperate: western Asia, Arabia, and China. Asia-tropical: India and Indo-China. Australasia: Australia. South America: Caribbean.

NOTES Eragrostideae. WDC.

Please cite this publication as detailed in How to Cite Version: 3rd February 2016.