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Descriptions

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

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

Poa piperi

HABIT Perennial; caespitose; clumped loosely. Rhizomes elongated. Butt sheaths glabrous. Basal innovations extravaginal and intravaginal. Culms erect, or geniculately ascending; 26–55 cm long. Culm-internodes terete, or elliptical in section (weakly). Leaf-sheaths open for most of their length; with 0.33–0.66 of their length closed; antrorsely scabrous; glabrous on surface, or pubescent; with reflexed hairs. Ligule an eciliate membrane; 1–2 mm long; scaberulous on abaxial surface; truncate, or obtuse. Collar glabrous, or pubescent. Leaf-blades involute; 20–40 cm long; 1–3 mm wide. Leaf-blade surface scabrous; rough adaxially. Leaf-blade margins scabrous. Leaf-blade apex abruptly acute; hooded.

INFLORESCENCE Dioecious. Inflorescence a panicle; comprising 18–60 fertile spikelets.

Panicle open; lanceolate, or ovate; equilateral, or nodding; 4–8 cm long. Primary panicle branches ascending; 1–2 -nate; 3–8 cm long; bearing 3–8 fertile spikelets on each lower branch. Panicle branches scabrous.

Spikelets solitary. Fertile spikelets pedicelled.

FERTILE SPIKELETS Spikelets comprising 2–5(–7) fertile florets; with diminished florets at the apex. Spikelets oblong; laterally compressed; 6–9(–11) mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes 1–2 mm long; smooth, or scaberulous. Floret callus woolly.

GLUMES Glumes persistent; similar; shorter than spikelet. Lower glume lanceolate; 4 mm long; 1 length of upper glume; membranous; 1-keeled; 3 -veined. Lower glume apex acute. Upper glume lanceolate; 4 mm long; 0.66–1 length of adjacent fertile lemma; membranous; 1-keeled; 3 -veined. Upper glume apex acute.

FLORETS Fertile florets female. Fertile lemma elliptic; 4–6(–7) mm long; membranous; keeled; 5 -veined. Lemma midvein scabrous. Lemma surface smooth, or scaberulous; glabrous. Lemma apex acute. Palea keels scabrous. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Anthers 3; 2–3 mm long.

MALE Male inflorescence similar to female. Male spikelets resembling female.

DISTRIBUTION North America: northwest USA and southwest USA.

NOTES Poeae. Fl N Amer 2007.

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