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Published In: Nova Genera et Species Plantarum seu Prodromus 1, 21. 1788. (Prodr.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 8/6/2009)


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56. Leersia Sw. (cutgrass, white grass)

(Pyrah, 1969)

Plants perennial, with rhizomes. Flowering stems ascending to spreading, sometimes rooting at the nodes, sometimes branched, circular in cross‑section or somewhat flattened, glabrous or hairy near the nodes. Leaves several per stem. Leaf sheaths mostly not overlapping, glabrous or roughened with minute, stiff, spinelike, downwardly pointing hairs, open for most of their length, the ligule membranous, glabrous, usually with an uneven margin. Leaf blades flat, glabrous to hairy, often roughened, with minute, stiff, spinelike, hairs, especially along the margins. Inflorescences open panicles with loosely ascending, spikelike branches. Spikelets numerous, minutely stalked, oriented toward 1 side of the inflorescence branches, strongly flattened, with 1 perfect floret. Glumes absent (actually reduced to a minute, cuplike structure at the spikelet base). Lemma 1, strongly keeled, narrowly to broadly oblong, the tip abruptly tapered to a point but awnless, papery, glabrous or hairy, sometimes with a noticeable fringe of hairs along the margins and keel, 5‑nerved. Paleas similar to and about as long as the lemmas, 3‑nerved. Stamens 2 or 3 (1 or 6 elsewhere). Fruits often somewhat flattened, uneven in outline, with 1 side nearly straight and the other curved, reddish brown. Seventeen species, nearly worldwide, most diverse in tropical regions.

Plants of Leersia are quite variable in size and habit, depending upon season and habitat. In L. lenticularis and L. oryzoides, the stiff, needlelike hairs of the leaves, especially along the margins, act as tiny sawteeth, giving rise to the common name “cutgrass,” as any person knows who has walked through a stand and been scratched or lacerated. The leaves of L. virginica are less formidable.


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1 Spikelets 3–4 mm wide, broadly oval to nearly circular in outline, 1.0–1.8 times as long as wide 1 Leersia lenticularis
+ Spikelets 0.8–2.0 mm wide, oblong to narrowly elliptic, 2.5–4.0 times as long as wide (2)
2 (1) Spikelets 4–7 mm long, 1.5–2.0 mm wide; stamens 3; stems not flattened; lowermost inflorescence branches 2–4 per node 3 Leersia oryzoides
+ Spikelets 3–4 mm long, 1.0–1.4 mm wide; stamens 2; stems often somewhat flattened; inflorescence branches all 1 per node 3 Leersia virginica
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