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GrassBase - The Online World Grass Flora
Descriptions
W.D. Clayton, M. Vorontsova, K.T. Harman & H. Williamson
© Copyright The Board of Trustees, Royal Botanic Gardens, Kew.
Stipa occidentalis
HABIT Perennial; caespitose; clumped densely. Culms 80–120 cm long. Culm-internodes distally glabrous, or pubescent. Leaf-sheaths glabrous on surface to pubescent. Ligule an eciliate membrane; 0.5–1 mm long; entire, or erose; truncate. Leaf-blades filiform, or linear; flat, or involute; 10–20 cm long; 1–5 mm wide. Leaf-blade surface glabrous, or puberulous. Leaf-blade apex hardened.
INFLORESCENCE Inflorescence a panicle.
Panicle open; linear; 5–30 cm long.
Spikelets solitary. Fertile spikelets pedicelled.
FERTILE SPIKELETS Spikelets comprising 1 fertile florets; without rhachilla extension. Spikelets lanceolate; subterete; 7–15 mm long; breaking up at maturity; disarticulating below each fertile floret. Floret callus elongated; curved; 1–1.5 mm long; pubescent; pungent.
GLUMES Glumes persistent; similar; exceeding apex of florets; thinner than fertile lemma. Lower glume lanceolate; 1 length of upper glume; membranous; without keels; 3–5 -veined. Lower glume apex acuminate. Upper glume lanceolate; 7–15 mm long; hyaline; without keels; 3–7 -veined. Upper glume apex acuminate.
FLORETS Fertile lemma lanceolate; subterete; 5–8 mm long; membranous; light brown; without keel; 5 -veined. Lemma surface pubescent; with conspicuous apical hairs. Lemma margins convolute; covering most of palea. Lemma hairs 0.5–1.5 mm long. Lemma apex acute; awned; 1 -awned. Principal lemma awn bigeniculate; 15–50 mm long overall; with twisted column. Middle segment of lemma awn glabrous, or hirtellous. Column of lemma awn hirsute; with 1 mm long hairs. Palea 2–3.5 mm long; 0.5 length of lemma; 2 -veined; without keels. Palea surface pubescent.
FLOWER Lodicules 3; 1.5 mm long. Anthers 3; 2.5 mm long. Stigmas 2. Ovary glabrous.
FRUIT Caryopsis with adherent pericarp. Hilum linear.
DISTRIBUTION North America: Subarctic, western Canada, northwest USA, north-central USA, southwest USA, and south-central USA.
NOTES Stipeae. Fl Pac NW 1994.
Please cite this publication as detailed in How to Cite Version: 3rd February 2016.
