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Descriptions

W.D. Clayton, M. Vorontsova, K.T. Harman & H. Williamson

© Copyright The Board of Trustees, Royal Botanic Gardens, Kew.

Hilaria rigida

HABIT Perennial. Rhizomes elongated. Culms decumbent; 50–100 cm long. Culm-internodes distally woolly. Culm-nodes glabrous, or pubescent. Leaf-sheaths longer than adjacent culm internode; smooth, or antrorsely scabrous. Leaf-sheath oral hairs woolly. Ligule an eciliate membrane; 1 mm long; pubescent on abaxial surface (woolly). Leaf-blades involute; 2–5 cm long; 2–4 mm wide; coriaceous; stiff. Leaf-blade surface ribbed; smooth, or scabrous; glabrous, or woolly. Leaf-blade apex pungent.

INFLORESCENCE Inflorescence composed of racemes.

Racemes borne along a central axis; closely spaced; in a multilateral false spike; cuneate; unilateral; 0.6–1.2 cm long; bearing a triad of spikelets. Central inflorescence axis 4–7 cm long. Rhachis obsolete; deciduous from axis. Raceme-bases brief; pilose.

Spikelets in threes. Fertile spikelets pedicelled; 1 in the cluster. Companion sterile spikelets sessile; 2 in the cluster.

STERILE SPIKELETS Companion sterile spikelets well-developed; male; cuneate; asymmetrical; dorsally compressed; 6–12 mm long; as long as fertile; deciduous with the fertile. Companion sterile spikelet glumes free; membranous; 5–9 mm long; 5–7 -veined; ciliate on margins; lobed; 2–4 -fid; mucronate. Companion sterile spikelet lemmas 2–4; exserted from glumes; 2–4 mm long; dentate; 1-awned; with 2 mm long awn.

FERTILE SPIKELETS Spikelets comprising 1 fertile florets; without rhachilla extension. Spikelets oblong; laterally compressed; 6–12 mm long; falling entire; deciduous with accessory branch structures.

GLUMES Glumes free; shorter than spikelet. Lower glume oblong; asymmetrical; membranous; pallid; 1-keeled; 7 -veined. Lower glume margins ciliate. Lower glume apex lobed; 2 -fid; awned; 1–3 -awned. Lower glume awn dorsal; 3–6 mm long. Upper glume oblong; asymmetrical; 0.75 length of adjacent fertile lemma; membranous; pallid; 1-keeled; 7 -veined. Upper glume margins ciliate. Upper glume apex lobed; 2 -fid; awned; 1–3 -awned. Upper glume awn dorsal; 3–6 mm long.

FLORETS Fertile florets bisexual. Fertile lemma lanceolate; laterally compressed; 6–12 mm long; membranous; keeled; 3 -veined. Lemma apex lobed; 2 -fid; incised 0.25 of lemma length; acute; awned; 1 -awned. Principal lemma awn from a sinus; 4 mm long overall.

FLOWER Lodicules 2; 0.1 mm long. Anthers 3; 4–4.5 mm long.

DISTRIBUTION North America: southwest USA and Mexico.

NOTES Cynodonteae. Swallen.

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