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Descriptions

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

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

Trisetum durangense

HABIT Perennial; caespitose. Rhizomes short. Culms 75–110 cm long; 3 -noded. Culm-nodes pubescent. Leaf-sheaths 11–23 cm long; subequal to internodes; pilose. Ligule an eciliate membrane; 3–7 mm long; lacerate; acute. Leaf-blades flat, or conduplicate; 15–50 cm long; 1–4 mm wide; stiff. Leaf-blade surface scabrous; rough on both sides. Leaf-blade margins ciliate.

INFLORESCENCE Inflorescence a panicle. Peduncle smooth, or retrorsely scabrous above.

Panicle open; pyramidal; nodding; 15–22 cm long; 5–20 cm wide. Primary panicle branches ascending; 4–6 -nate; whorled at most nodes (4–5 whorls); 3–14 cm long. Panicle axis scabrous. Panicle branches capillary; scabrous.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels scabrous.

FERTILE SPIKELETS Spikelets comprising 2–3 fertile florets; with a barren rhachilla extension. Spikelets oblong; laterally compressed; 7–9 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes 2 mm long; pubescent. Floret callus pubescent. Floret callus hairs 1 mm long.

GLUMES Glumes persistent; similar; with lower narrower than upper; reaching apex of florets; thinner than fertile lemma; shiny; gaping. Lower glume lanceolate; 5–6 mm long; 0.7–0.8 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume primary vein scabrous. Lower glume apex acute. Upper glume lanceolate; 6–9 mm long; 0.9–1.1 length of adjacent fertile lemma; membranous; 1-keeled; 3 -veined. Upper glume apex acute.

FLORETS Fertile lemma elliptic; 7–8 mm long; membranous; shiny; keeled; 5 -veined. Lemma lateral veins prominent (above); excurrent. Lemma surface pilose. Lemma apex dentate; 2 -fid; awned; 1 -awned. Principal lemma awn dorsal; arising 0.5 way up back of lemma; geniculate; 7–10 mm long overall; with twisted column. Palea gaping; 5.8–7 mm long; hyaline. Palea keels ciliate.

FLOWER Lodicules 2; 0.7–1.1 mm long; ciliate. Anthers 3; 2–3 mm long. Ovary pubescent on apex.

FRUIT Caryopsis with adherent pericarp; 2–2.7 mm long.

DISTRIBUTION North America: Mexico.

NOTES Aveneae. Finot & Peterson 2005.

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