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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 helmsii

HABIT Perennial; caespitose. Rootstock evident. Butt sheaths herbaceous; pallid. Basal innovations intravaginal. Culms 50–150 cm long; 3–6 mm diam. Culm-internodes elliptical in section; smooth. Culm-nodes glabrous. Lateral branches lacking. Leaves mostly basal. Leaf-sheaths loose; keeled; antrorsely scabrous; glabrous on surface. Ligule a ciliolate membrane; 0.5–2 mm long; pubescent on abaxial surface; truncate. Leaf-blades 5–50 cm long; 3–8 mm wide; light green. Leaf-blade midrib conspicuous. Leaf-blade surface grooved on either side of midline; scabrous; glabrous. Leaf-blade margins scabrous. Leaf-blade apex acute.

INFLORESCENCE Inflorescence a panicle. Peduncle antrorsely scabrous above.

Panicle open; lanceolate; 15–35 cm long. Primary panicle branches spreading; 5–7 -nate; 4–12 cm long. Panicle branches scabrous.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels scabrous.

FERTILE SPIKELETS Spikelets comprising 3–8 fertile florets; with diminished florets at the apex. Spikelets oblong; laterally compressed; 5–8 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes smooth. Floret callus woolly.

GLUMES Glumes persistent; similar; shorter than spikelet. Lower glume oblong; 0.9 length of upper glume; membranous; 1-keeled; 3 -veined. Lower glume primary vein scabrous. Lower glume apex obtuse to acuminate. Upper glume oblong; 0.5–0.66 length of adjacent fertile lemma; membranous; 1-keeled; 3 -veined. Upper glume primary vein scabrous. Upper glume apex obtuse to acuminate.

FLORETS Fertile lemma lanceolate; elliptic in profile; 2.75–3.75 mm long; membranous; keeled; 5 -veined. Lemma midvein ciliate; hairy below. Lemma surface pilose; hairy at base; hairy on veins. Lemma apex obtuse. Palea 0.9 length of lemma. Palea keels scaberulous; adorned above. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; membranous. Anthers 3; 2 mm long; yellow, or purple.

FRUIT Caryopsis with adherent pericarp. Hilum punctiform.

DISTRIBUTION Australasia: Australia.

NOTES Poeae. Vickery.

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