Panicum rivale

HABIT Annual. Culms decumbent; 5–20 cm long; rooting from lower nodes. Culm-internodes distally glabrous. Culm-nodes glabrous, or pubescent, or bearded. Leaf-sheaths mostly shorter than adjacent culm internode; striately veined; glabrous on surface; outer margin hairy. Ligule an eciliate membrane; 1 mm long. Leaf-blade base cordate. Leaf-blades lanceolate, or ovate; 16–28 cm long; 2–4 mm wide. Leaf-blade surface pilose; hairy on both sides; with tubercle-based hairs. Leaf-blade apex acuminate.

INFLORESCENCE Inflorescence a panicle. Peduncle 2–6 cm long; glabrous.

Panicle open; ovate; 3–8 cm long. Primary panicle branches spreading, or reflexed; distant. Panicle branches flexuous; eglandular.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels filiform; flexuous.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets elliptic, or obovate; dorsally compressed; 1.1–1.6 mm long; 0.5–0.6 mm wide; falling entire.

GLUMES Glumes shorter than spikelet, or reaching apex of florets; thinner than fertile lemma. Lower glume ovate; 0.7–0.8 mm long; 0.5–0.66 length of spikelet; membranous; without keels; 1–3 -veined. Lower glume lateral veins absent, or distinct; transversely connected at apex. Lower glume apex acute. Upper glume ovate; 0.9–1 length of spikelet; membranous; without keels; 5 -veined. Upper glume surface pubescent. Upper glume apex obtuse.

FLORETS Basal sterile florets barren; without significant palea. Lemma of lower sterile floret similar to upper glume; ovate; 1 length of spikelet; membranous; 5 -veined; puberulous; acute. Fertile lemma elliptic; dorsally compressed; 1–1.2 mm long; indurate; pallid; without keel. Lemma surface smooth. Lemma margins involute. Palea involute; indurate.

DISTRIBUTION South America: northern South America.

NOTES Paniceae. Fl Guiana 1995.

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