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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 infirma

HABIT Annual; caespitose. Butt sheaths herbaceous. Culms erect, or geniculately ascending, or decumbent; 1–25 cm long; 1–3 -noded. Culm-internodes terete; smooth. Lateral branches lacking, or sparse. Leaves mostly basal. Leaf-sheaths keeled; smooth. Ligule an eciliate membrane; 2–3 mm long; obtuse. Leaf-blades flat, or conduplicate; 0.5–8 cm long; 1–4 mm wide. Leaf-blade surface smooth; glabrous. Leaf-blade margins scaberulous. Leaf-blade apex obtuse, or abruptly acute; hooded.

INFLORESCENCE Inflorescence a panicle.

Panicle open; lanceolate, or ovate; dense, or loose; 0.5–10 cm long. Primary panicle branches spreading; 1–2 -nate. Panicle branches smooth.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels 0.3–3 mm long.

FERTILE SPIKELETS Spikelets comprising 2–4 fertile florets; with diminished florets at the apex. Spikelets oblong, or ovate; laterally compressed; 2–4 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes eventually visible between lemmas; smooth. Floret callus pubescent.

GLUMES Glumes persistent; similar; shorter than spikelet. Lower glume ovate; 1–1.5 mm long; 0.6–0.7 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume lateral veins absent. Lower glume apex acute. Upper glume elliptic, or oblong; 1.3–2.5 mm long; 0.9–1 length of adjacent fertile lemma; membranous; 1-keeled; 1–3 -veined. Upper glume apex obtuse.

FLORETS Fertile lemma ovate; elliptic in profile; 2–2.5 mm long; membranous; much thinner above; much thinner on margins; keeled; 5 -veined. Lemma lateral veins stopping well short of apex. Lemma surface pubescent; hairy below; hairy on veins. Lemma apex obtuse. Palea 1 length of lemma. Palea keels woolly; adorned above. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; membranous. Anthers 3; 0.2–0.5 mm long.

FRUIT Caryopsis with adherent pericarp. Hilum punctiform.

DISTRIBUTION Europe: northern, central, southwestern, and southeastern. Africa: north and Macaronesia. Asia-temperate: Soviet Middle Asia, Caucasus, western Asia, Arabia, and China. Asia-tropical: India. Australasia: Australia and New Zealand. North America: western Canada, northwest USA, southwest USA, southeast USA, and Mexico. South America: western South America.

NOTES Poeae. CEH.

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