Acroceras excavatum

HABIT Perennial. Culms decumbent; 100–200 cm long; rooting from lower nodes. Culm-internodes 3–11 cm long. Culm-nodes brown; glabrous. Lateral branches sparse. Leaf-sheaths 4–7 cm long; glabrous on surface, or pubescent; with tubercle-based hairs; outer margin hairy. Ligule an eciliate membrane; 2–4.5 mm long; brown; pubescent on abaxial surface; truncate. Leaf-blade base simple. Leaf-blades linear, or lanceolate; 15–20 cm long; 12–16 mm wide. Leaf-blade midrib conspicuous. Leaf-blade surface glabrous, or pilose; sparsely hairy; hairy on both sides. Leaf-blade margins scaberulous. Leaf-blade apex acuminate.

INFLORESCENCE Inflorescence a panicle.

Panicle open; pyramidal; 20–40 cm long; 10–30 cm wide; contracted about primary branches. Primary panicle branches 4–15 cm long; bearing spikelets almost to the base. Panicle axis scabrous.

Spikelets solitary, or in pairs. Fertile spikelets pedicelled; 2 in the cluster. Pedicels filiform; 5–15 mm long; pubescent.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets elliptic; laterally compressed; 3.3–3.8 mm long; 1.3–1.6 mm wide; falling entire. Spikelet callus square; 0.3 mm long; base truncate.

GLUMES Glumes dissimilar; shorter than spikelet; thinner than fertile lemma. Lower glume ovate; clasping; 1.7–2.1 mm long; 0.5 length of spikelet; membranous; without keels; 3 -veined. Lower glume surface smooth, or asperulous; glabrous, or pubescent. Lower glume apex obtuse. Upper glume elliptic; 2.8–3.5 mm long; 0.9 length of spikelet; membranous; 5 -veined. Upper glume surface asperulous; rough on veins. Upper glume apex obtuse.

FLORETS Basal sterile florets barren; without significant palea. Lemma of lower sterile floret similar to upper glume; oblong; 3.1–3.6 mm long; 1 length of spikelet; membranous; 5 -veined; obtuse. Fertile lemma elliptic; dorsally compressed; 2.9–3.5 mm long; 1.2–1.6 mm wide; indurate; dark brown. Lemma surface papillose. Lemma margins involute. Lemma apex obtuse; pubescent, with a shallow excavation, and with a green spot. Palea elliptic; involute; 1 length of lemma; indurate. Palea apex pubescent.

FRUIT Caryopsis with adherent pericarp; ellipsoid; 2.1 mm long; dark brown. Embryo 0.5 length of caryopsis. Hilum punctiform. Disseminule comprising a spikelet.

DISTRIBUTION South America: northern South America, western South America, Brazil, and southern South America.

NOTES Paniceae. Fl Paraguay 1997.

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