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.

Bromus orcuttianus

HABIT Perennial; caespitose; clumped loosely. Culms erect; 90–150 cm long; 2–4 -noded. Culm-internodes distally pruinose, or pubescent. Culm-nodes brown; pubescent. Leaf-sheaths tubular for much of their length; 3.5–11 cm long; mostly shorter than adjacent culm internode; pilose. Leaf-sheath oral hairs ciliate; 2–3 mm long. Ligule an eciliate membrane; 1–3 mm long; glabrous on abaxial surface, or pilose on abaxial surface; erose; obtuse. Leaf-blades 7–24 cm long; 3–12 mm wide. Leaf-blade surface glabrous. Leaf-blade margins smooth, or scaberulous.

INFLORESCENCE Inflorescence a panicle.

Panicle open; lanceolate, or pyramidal; 7–13.5 cm long; 2–10 cm wide. Primary panicle branches appressed, or ascending, or spreading; 1–2(–3) -nate; 3–7.5 cm long; bearing 1–5 fertile spikelets on each lower branch.

Spikelets solitary. Fertile spikelets pedicelled.

FERTILE SPIKELETS Spikelets comprising 3–9 fertile florets; with diminished florets at the apex. Spikelets oblong; laterally compressed; 20–37 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes eventually visible between lemmas.

GLUMES Glumes persistent; shorter than spikelet. Lower glume lanceolate; 5–9 mm long; 0.75 length of upper glume; membranous; without keels; 1(–3) -veined. Lower glume lateral veins absent, or obscure. Lower glume surface glabrous. Lower glume apex acute. Upper glume lanceolate; 7–11 mm long; 0.75 length of adjacent fertile lemma; membranous; without keels; 3 -veined. Upper glume surface glabrous. Upper glume apex acute; muticous, or mucronate.

FLORETS Fertile lemma oblong; 9–15 mm long; chartaceous; without keel, or keeled; lightly keeled; 5–7 -veined. Lemma lateral veins obscure. Lemma surface glabrous, or puberulous. Lemma apex dentate; 2 -fid; with lobes 0.1–0.2 mm long; awned; 1 -awned. Principal lemma awn subapical; (4–)5.5–8 mm long overall. Palea 8–11 mm long. Palea surface glabrous, or puberulous; hairy on back and on margins. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; membranous. Anthers 3; 3.5 mm long; yellow, or orange. Ovary with a fleshy appendage above style insertion; pubescent on apex.

FRUIT Caryopsis with adherent pericarp; linear; 6–9 mm long; dark brown, or purple; hairy at apex; apex fleshy. Hilum linear.

DISTRIBUTION North America: northwest USA and southwest USA.

NOTES Bromeae. Saarela et al 2006.

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