Leersia

Plants usually perennial, rarely annual; terrestrial or aquatic; rhizomatous or cespitose; synoecious. Culms 20-150 cm (occasionally longer in floating mats), erect or decumbent, often rooting at the nodes, branched or unbranched. Leaves equitably distributed along the culm; sheaths open; auricles absent; ligules membranous; pseudopetioles absent; blades aerial, linear to broadly lanceolate, flat or folded, sometimes involute when dry. Inflorescences terminal panicles, usually exserted, axillary panicles sometimes also present; disarticulation beneath the spikelets. Spikelets bisexual, with 1 floret; florets laterally compressed, linear to suborbicular in sideview. Glumes absent; calluses not stipelike, glabrous; lemmas and paleas subequal, chartaceous to coriaceous, ciliate-hispid or glabrous, tightly clasping along the margins; lemmas 5-veined, obtuse or acute to acuminate, sometimes mucronate, usually unawned; paleas 3-veined, unawned; lodicules 2; anthers 1, 2, 3, or 6; styles 2, bases fused, stigmas laterally exserted, plumose. Caryopses laterally compressed; embryos about 1/3 as long as the caryopses; hila linear, x = 12.

Distribution

Conn., N.J., N.Y., Wash., Va., Del., D.C, Wis., W.Va., Md., Fla., Wyo., N.H., N.Mex., Tex., La., Tenn., N.C., S.C., Pa., Nev., Mass., Maine, R.I., Vt., Puerto Rico, Colo., Calif., Ala., Kans., N.Dak., Nebr., Okla., S.Dak., Miss., Ark., Ill., Ga., Ind., Iowa, Ariz., Idaho, Ohio, Utah, Mo., Minn., Mich., Mont., Ky., Oreg., B.C., Man., N.B., N.S., Ont., P.E.I., Que., Sask.

Discussion

Leersia is a genus of about 17 aquatic to mesophytic species, growing primarily in tropical and warm-temperate regions. Five species are native to the Flora region. Leersia is closely allied to Oryza. It is unusual in the variability in stamen numbers among its species.

Selected References

Pyrah, G.L. 1969. Taxonomic and distributional studies in Leersia (Gramineae). Iowa State Coll. J. Sci. 44:215-270.

Lower Taxa

Leersia hexandra, Leersia lenticularis, Leersia monandra, Leersia oryzoides, Leersia virginica

Key

1	Spikelets 1.5-2 mm long, glabrous; plants not rhizomatous	Leersia monandra
1	Spikelets 2.5-6.5 mm long, usually ciliate on the margins and keel, and glabrous or pubescent elsewhere; plants rhizomatous.	> 2
2	Spikelets nearly as wide as long	Leersia lenticularis
2	Spikelets not more than 1/2 as wide as long.	> 3
3	Anthers 2; spikelets 2.5-3.6 mm long; panicle branches single at all nodes	Leersia virginica
3	Anthers 3 or 6; spikelets 3.2-6.5 mm long; panicle branches 1-2 or more at the lower nodes, single at the upper nodes.	> 4
4	Panicles exserted, 5-15 cm long; branches appressed to ascending, spikelet-bearing to near the base; anthers 6; spikelets 3.2-4.7(5) mm long	Leersia hexandra
4	Panicles exserted or enclosed, 10-30 cm long; branches spreading on exserted panicles, naked on the lower 1/3; anthers 3; spikelets (4)4.2-6.5 mm long	Leersia oryzoides