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Descriptions

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

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

Sorghastrum contractum

HABIT Perennial; caespitose. Culms erect; 120–230 cm long; 2–4 mm diam. Leaf-sheaths 15–40 cm long. Ligule an eciliate membrane; 2–3.5 mm long. Leaf-blades flat, or convolute; 25–50 cm long; 2–8 mm wide. Leaf-blade surface scabrous; glabrous, or pubescent; hairy abaxially. Leaf-blade margins scabrous.

INFLORESCENCE Inflorescence a panicle with branches tipped by a raceme. Peduncle 30–50 cm long.

Panicle contracted; linear; 15–35 cm long. Panicle axis glabrous.

Racemes bearing a triad of spikelets, or few fertile spikelets; 1–2 fertile spikelets on each. Rhachis fragile at the nodes. Rhachis internodes filiform.

Spikelets in pairs, or in threes. Fertile spikelets sessile; 1 in the cluster. Companion sterile spikelets pedicelled; 1 in the cluster, or 2 in the cluster. Pedicels filiform; 2.5–4 mm long; glabrous.

STERILE SPIKELETS Companion sterile spikelets represented by barren pedicels.

FERTILE SPIKELETS Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets lanceolate; dorsally compressed; 4–6 mm long; falling entire; deciduous with accessory branch structures. Spikelet callus cuneate; pilose; base pungent.

GLUMES Glumes dissimilar; firmer than fertile lemma. Lower glume oblong; 1 length of spikelet; coriaceous; without keels; 7–9 -veined. Lower glume surface pubescent. Lower glume apex truncate. Upper glume oblong; 1 length of spikelet; coriaceous; without keels; 5 -veined. Upper glume surface glabrous. Upper glume apex acute.

FLORETS Basal sterile florets barren; without significant palea. Lemma of lower sterile floret oblong; 3.5–5 mm long; hyaline; 2 -veined; ciliate on margins; dentate; 2 -fid. Fertile lemma oblong; 2.6–4 mm long; hyaline; without keel; 3 -veined. Lemma margins ciliolate. Lemma apex lobed; 2 -fid; awned; 1 -awned. Principal lemma awn from a sinus; bigeniculate; 18–35 mm long overall; with twisted column. Column of lemma awn hispidulous. Palea absent or minute.

FLOWER Lodicules 2; glabrous. Anthers 3; 2–3 mm long.

DISTRIBUTION South America: Brazil.

NOTES Andropogoneae. Davila 1993.

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