GrassBase - The Online World Grass Flora


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

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

Bouteloua williamsii

HABIT Perennial; caespitose. Culms erect; 35–90 cm long. Ligule a fringe of hairs. Leaf-blades 10–25 cm long; 1.5–2.5 mm wide.

INFLORESCENCE Inflorescence composed of racemes.

Racemes 7–14; borne along a central axis; ascending; unilateral; 2–4 cm long; bearing 9–20 fertile spikelets on each. Central inflorescence axis 6–15 cm long. Rhachis deciduous from axis; flattened; pubescent on margins; terminating in a barren extension; extension bristle-like. Spikelet packing broadside to rhachis.

Spikelets ascending; solitary. Fertile spikelets sessile.

FERTILE SPIKELETS Spikelets comprising 1 fertile florets; with diminished florets at the apex. Spikelets cuneate; laterally compressed; 4.5–6 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus glabrous, or pilose. Floret callus pubescent.

GLUMES Glumes similar; exceeding apex of florets, or reaching apex of florets; thinner than fertile lemma; gaping. Lower glume lanceolate; 2.5–4.5 mm long; 0.5–0.8 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume primary vein scaberulous. Lower glume lateral veins absent. Lower glume apex acuminate. Upper glume lanceolate; 4.5–6 mm long; 1–1.1 length of adjacent fertile lemma; membranous; 1-keeled; 1 -veined. Upper glume primary vein scaberulous. Upper glume lateral veins absent. Upper glume apex acuminate.

FLORETS Fertile lemma elliptic; 4–6 mm long; coriaceous; without keel; 3 -veined. Lemma surface glabrous, or puberulous. Lemma apex dentate; 3 -fid; awned; 3 -awned. Principal lemma awn 2–3 mm long overall. Lateral lemma awns arising on apex of lobes; 0.5–1.5 mm long; shorter than principal. Palea surface pubescent; hairy on back. Palea apex with excurrent keel veins. Rhachilla extension pilose; hairy at tip. Apical sterile florets 1 in number; male; oblong; 3–5 mm long. Apical sterile lemmas glabrous, or pubescent; dentate; 3 -fid; acute; awned; 3 -awned. Apical sterile lemma awns 4–7 mm long.

FRUIT Caryopsis with adherent pericarp.

DISTRIBUTION North America: Mexico. South America: Mesoamericana.

NOTES Cynodonteae. Gould.

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