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Descriptions

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

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

Panicum longissimum

HABIT Perennial. Cataphylls evident. Rhizomes elongated. Culms erect; 150–200 cm long. Culm-internodes terete; 30 cm long; distally glabrous. Culm-nodes glabrous. Lateral branches ample. Leaf-sheaths 10–30 cm long; keeled; striately veined; glabrous on surface; outer margin hairy. Ligule a ciliate membrane; 2–2.4 mm long. Collar dark; pubescent. Leaf-blades linear, or lanceolate; 50–80 cm long; 5–9 mm wide; stiff. Leaf-blade surface pubescent; hairy adaxially.

INFLORESCENCE Inflorescence a panicle. Peduncle 40–50 cm long; pubescent above.

Panicle contracted; linear; 10–30 cm long; contracted about primary branches. Primary panicle branches appressed. Panicle axis angular; scaberulous. Panicle branches scabrous; glabrous in axils, or pubescent in axils.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels scabrous; glabrous, or ciliate.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets elliptic; dorsally compressed; 2–3.3 mm long; 1.2 mm wide; falling entire; readily shedding fertile florets.

GLUMES Glumes reaching apex of florets; thinner than fertile lemma. Lower glume ovate; clasping; 1.5–1.7 mm long; 0.5 length of spikelet; membranous; without keels; 5 -veined. Lower glume primary vein scabrous. Lower glume apex acute. Upper glume ovate; 1 length of spikelet; membranous; without keels; 7 -veined. Upper glume primary vein scabrous. Upper glume lateral veins prominent. Upper glume surface pubescent; hairy above; inner surface pubescent. Upper glume apex acute.

FLORETS Basal sterile florets male; with palea. Lemma of lower sterile floret similar to upper glume; ovate; 1 length of spikelet; membranous; 9 -veined; prominently veined; pubescent; hairy above; acute. Palea of lower sterile floret 2.5 mm long. Fertile lemma ovate; dorsally compressed; 2.4 mm long; 1 mm wide; indurate; yellow; shiny; without keel. Lemma surface smooth. Lemma margins involute. Palea involute; indurate. Palea surface papillose.

FRUIT Caryopsis with adherent pericarp.

DISTRIBUTION South America: southern South America.

NOTES Paniceae. Fl Paraguay 1997.

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