Flora of the Southeastern United States
2022 Edition

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Key to Eleocharis, Key D: spikerushes with achenes lenticular or biconvex and styles 2-branched

1 Apex of sheath thin, membranous, hyaline, often with a torn edge.
..2 Culms 0.1-0.3 mm in diameter; achenes whitish to pale brown; leaf sheaths of the upper culm closely sheathing the stem, not wrinkled, the apex acute
..2 Culms 0.3-0.6 mm in diameter; achenes rufous- or olivaceous-brown to black; leaf sheaths of the upper culm usually prominently wrinkled, inflated, membranous, and disintegrating.
....3 Achenes rufous-brown to reddish-purple to black, (0.3-) 0.4-0.6 mm wide; longer bristles retrorsely barbed, shorter than to equaling achene body
....3 Achenes olivaceous-brown to black, 0.5-0.7 (-0.8) mm wide; longer bristles either retrorsely barbed and equaling to exceeding the tubercle, or smooth and shorter than the tubercle.
......4 Bristles retrorsely barbed, the longer equaling to exceeding the tubercle; [wet sandy or peaty habitats, widespread]
......4 Bristles smooth, the longer shorter than the tubercle; plants of [tidal rivers, in s. NJ]
1 Apex of sheath firm, somewhat thickened, opaque, with a definite edge.
........5 Rhizomatous perennials growing from thick horizontal rhizomes.
..........6 Basal (sterile) scales 2-3, the lowest not encircling the base of the spike; [of the Mountains, rarely the Piedmont]
..........6 Basal (sterile) scale solitary and spathiform, encircling the base of the spike; [of either the Mountains, upper Piedmont, or outer Coastal Plain].
............ 7 Achenes prominently reticulate-pitted; [of the outer Coastal Plain]
............ 7 Achenes smooth to faintly reticulate; [of the Mountains, rarely Piedmont, or outer Coastal Plain].
............ ..8 Culms slender to filiform; scales obtuse, 30-40 per spike; [of basic soils, of the Mountains and rarely Piedmont]
............ ..8 Culms thicker, somewhat inflated; scales acute, 5-30 per spike; [of brackish habitats of the outer Coastal Plain]
........5 Tufted or cespitose annuals without thick horizontal rhizomes.
............ ....9 Tubercle nearly or actually as broad as the achene, and appearing confluent with it, broader than high.
............ ......10 Tubercle flat-deltoid, 1/4 as high as the achene; bristles shorter than the achene body; [plants of clay soils only]
............ ......10 Tubercle short-conic, 1/3-1/2 as high as the achene; bristles much exceeding the tubercle; [plants of a variety of soils]
............ ....9 Tubercle < 2/3 as broad as the achene, conic, taller than broad.
............ ........11 Achene body pale brown, about 1 mm long
............ ........11 Achene body black, 0.5-1.0 mm long.
............ ..........12 Spikes lance-ovoid to subcylindric; achene body -.5-0.6 mm long
............ ..........12 Spikes ovoid to subglobose; achene body 0.7-1.0 mm long