Eleocharis melanocarpa
Eleocharis coloradoensis
black-fruit spike-rush, black-fruit spikesedge
dwarf spike-rush
to 2 times wider than thick, 35–60(–70) cm × 0.5–1.3 mm, hard, usually with to 10 blunt ribs, at 20X often finely ridged and minutely granular.
distal leaf sheaths brown to reddish.
3–12 × 3–4 mm;
proximal scale amplexicaulous, 3.5–4 mm, midrib region very broad and fleshy, apex entire;
subproximal scale with a flower;
floral scales 30–40, 8–10 per mm of rachilla, orange-brown to stramineous, midrib region stramineous, broadly ovate, papery or sometimes membranous, 3–4 × 2 mm, apex entire, rounded.
3–6 × 1–1.5 mm;
proximal scale 1/2 or less of spikelet length;
floral scales 6–25 per spikelet, mostly bright orange-brown, sometimes stramineous, 1.7–2.5 mm, apex subacute.
perianth bristles present, sometimes rudimentary, brown, length variable, obscurely retrorsely spinulose;
anthers brown, 1.7–2.2 mm.
perianth bristles mostly absent or rudimentary, occasionally to 5, 1/2 of achene length, very unequal;
anthers 0.6–0.9 mm.
subdeltoid in outline, sometimes broadly obpyriform, equilaterally trigonous, angles prominent, 0.9–1.2 × 0.7–1.1 mm, apex truncate.
medium to dark brown, obovoid to obpyriform, thickly trigonous, rarely some biconvex, angles distinct to prominent, faces convex or some plane, 0.75–1.1 × 0.55–0.7 mm, apex narrowly truncate or tapered into tubercle, rugulose at 10X to finely rough at 30X.
sessile, depressed-pyramidal, often apiculate, as wide as achene, 0.3–0.5 × 0.7–1.1 mm.
0.05–0.2 × 0.15 mm.
terminating rhizomes, 2.5–4 × 0.7–1.5 mm, body (apart from apical bud) broadly oblong to orbicular, not markedly curved.
Eleocharis melanocarpa
Eleocharis coloradoensis
Eleocharis melanocarpa is reported from Rhode Island; I have not seen a voucher specimen.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Most authors, except C. L. Gilly (1941), H. L. Mason (1957), and R. R. Yeo (1980), have included Eleocharis coloradoensis in E. parvula or E. parvula var. anachaeta. In typical E. coloradoensis, which occurs from Saskatchewan south to Kansas and in California to 2100 m elevation, the achenes are usually distinctly rugulose or rough, often pitted-cellular, their apices usually truncate, and the tubercles are usually brown, often rudimentary, clearly distinct from the achene, and apparently partly sunken into the achene summit. Some plants from the southern Great Plains to the Mexican border, including the type of E. parvula var. anachaeta from Louisiana, may deserve taxonomic recognition. They differ from typical E. coloradoensis in having nearly smooth achenes with the apex tapered to a tubercle that is difficult to distinguish from the achene. C. L. Gilly (1941) separated these plants as E. membranacea (Buckley) Gilly; application of that name is doubtful because achenes are lacking from the type. R. R. Yeo (1980) studied the life-history of E. coloradoensis in the Sacramento Valley, California, and showed that it can be used to control several aquatic weeds in irrigation canals. The n = 4 count reported from Kansas under E. parvula var. anachaeta (Anonymous 1964) and on voucher specimens at GH and UC, is probably erroneous; the label on a duplicate voucher specimen at NDA includes the information “n = 3 II’s + a chain of IV” (i.e., n = 5). The record from Washington is somewhat doubtful because the specimen lacks achenes. Literature reports of E. parvula from Illinois and Tennessee may refer to E. coloradoensis; I have not seen specimens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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