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Descriptions

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

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

Stipa porteri

HABIT Perennial. Culms erect; 20–35 cm long; 1 -noded. Leaf-sheaths smooth; glabrous on surface. Ligule an eciliate membrane; 2–3 mm long; glabrous on abaxial surface, or pubescent on abaxial surface; bilobed. Leaf-blades filiform; terete; 2–12 cm long; 0.5 mm wide. Leaf-blade surface grooved along midline; scaberulous.

INFLORESCENCE Inflorescence a panicle.

Panicle open; elliptic; 5–8 cm long. Primary panicle branches 2 -nate; simple, or sparsely divided; rebranched at middle; 1–3 cm long. Panicle branches capillary; flexuous; smooth.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels ciliate; hairy at tip.

FERTILE SPIKELETS Spikelets comprising 1 fertile florets; without rhachilla extension. Spikelets lanceolate; subterete; 5 mm long; breaking up at maturity; disarticulating below each fertile floret. Floret callus evident; 0.5 mm long; pubescent; obtuse.

GLUMES Glumes persistent; similar; reaching apex of florets; thinner than fertile lemma. Lower glume elliptic; 1 length of upper glume; membranous; purple; without keels; 5 -veined. Lower glume surface asperulous; rough at apex. Lower glume margins ciliate. Lower glume apex emarginate, or obtuse. Upper glume elliptic; 25–40 mm long; membranous; purple; without keels; 5 -veined. Upper glume surface asperulous; rough at apex. Upper glume margins ciliate. Upper glume apex emarginate, or obtuse.

FLORETS Fertile lemma lanceolate; subterete; 5 mm long; coriaceous; without keel; 5 -veined. Lemma lateral veins obscure. Lemma surface scaberulous; rough above; pubescent; hairy below. Lemma margins convolute; covering most of palea. Lemma apex emarginate; pubescent; awned; 1 -awned. Principal lemma awn bigeniculate; 12–15 mm long overall; with 8–10 mm long limb; with a straight or slightly twisted column; limb puberulous. Column of lemma awn 4–5 mm long; ciliate; with 1–2 mm long hairs. Palea 1 length of lemma; 2 -veined; without keels.

FLOWER Lodicules 3. Anthers 3. Stigmas 2. Ovary glabrous.

FRUIT Caryopsis with adherent pericarp. Hilum linear.

DISTRIBUTION North America: northwest USA.

NOTES Stipeae. N Amer Fl 1994.

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