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Descriptions

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

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

Bouteloua annua

HABIT Annual; caespitose. Culms geniculately ascending, or decumbent; slender; 10–25 cm long. Lateral branches ample; arising from lower culm and mid culm. Leaf-sheaths glabrous on surface; outer margin glabrous, or hairy. Ligule a fringe of hairs; 0.2 mm long. Leaf-blades 2–4 cm long; 1.5–3 mm wide. Leaf-blade surface glabrous, or pubescent; hairy adaxially. Leaf-blade margins ciliate; hairy at base.

INFLORESCENCE Inflorescence composed of racemes.

Racemes 3–7; borne along a central axis; unilateral; 2.5–3 cm long; bearing few fertile spikelets; bearing 4–7 fertile spikelets on each. Central inflorescence axis tip subulate. Rhachis deciduous from axis; angular; glabrous on margins; terminating in a barren extension; extension subulate. Spikelet packing broadside to rhachis; lax.

Spikelets appressed; solitary. Fertile spikelets sessile.

FERTILE SPIKELETS Spikelets comprising 1 fertile florets; with diminished florets at the apex. Spikelets cuneate; laterally compressed; 7–9 mm long; falling entire; deciduous with accessory branch structures.

GLUMES Glumes similar; shorter than spikelet; thinner than fertile lemma; gaping. Lower glume lanceolate; 3.5–4 mm long; 0.5–0.6 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume primary vein smooth, or scaberulous. Lower glume lateral veins absent. Lower glume apex acute to setaceously attenuate. Upper glume lanceolate; 6–8 mm long; 0.8–0.9 length of adjacent fertile lemma; membranous; 1-keeled; 1 -veined. Upper glume primary vein smooth, or scaberulous. Upper glume lateral veins absent. Upper glume apex acute to setaceously attenuate.

FLORETS Fertile lemma ovate; 7–9 mm long; coriaceous; keeled; 3 -veined. Lemma surface scabrous; rough above; pubescent; hairy at base. Lemma apex dentate; 3 -fid; mucronate; 3 -awned (mucros). Rhachilla extension glabrous. Apical sterile florets 1 in number; barren; rudimentary. Apical sterile lemmas awned; 3 -awned. Apical sterile lemma awns equal; 5–8 mm long; ciliate (below).

FRUIT Caryopsis with adherent pericarp.

DISTRIBUTION North America: Mexico.

NOTES Cynodonteae. Gould.

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