Eleocharis engelmannii
Eleocharis cancellata
Engelman spikerush, Engelmann's spike-rush, Engelmann's spikesedge, englemann's spike-rush
Arizona spikerush
2–40 cm × 0.5–1.5(–2) mm.
mostly ascending, terete or 4-angled, 2 cm × 0.2–0.3 mm, soft.
apex of distal leaf sheath obtuse to acute, tooth to 0.3 mm.
distal leaf sheaths persistent, greenish to whitish, translucent, membranous, apex blunt.
lanceoloid to subcylindric or ovoid, 5–10(–20) × 2–3(–4) mm, apex acute (to rounded);
proximal scale empty, encircling ca. 2/3 of culm;
floral scales 25–100(–200), 8–12 per mm of rachilla, orangebrown to stramineous, 2(–2.5) × 1–1.3 mm, midribs mostly keeled, ovate, apex narrowly rounded to subacute.
ovoid, 2–3 × 1 mm, apex acute;
floral scales 7–10, 5 per mm of rachilla, bright brown or colorless, medially greenish, ovate to lanceolate, not folded lengthwise, 0.8–1.2(–1.5) × 0.6–0.8 mm, midrib obscure to slightly keeled, apex acute to acuminate.
perianth bristles present or often absent, 5–8, brown, stout, rudimentary to slightly exceeding tubercle;
stamens (2–)3;
anthers brown to yellow, 0.3–0.7(–1) mm;
styles 2–3-fid.
perianth bristles absent;
anthers orange-brown, 0.2–0.3 mm.
0.9–1.1(–1.5) × 0.7–1.1 mm.
brownish, broadly ovoid to obpyriform, much less than 2 times longer than wide, with angles plus longitudinal ridges ca. 6, rather obscure, 0.5–0.55 × 0.35 mm, apex blunt, trabeculae 15–20, distinct.
depressed, subdeltoid, 0.1–0.3(–0.4) × 0.6–0.9(–1) mm, 1/10–2/5 as high as wide, 1/4 or less as high as achene, 9/10 as wide as achene, very rarely 2/5 as high as achene (in E. engelmannii var. robusta).
grayish or brownish, often appressed, mostly pyramidal, 0.1 × 0.1 mm.
= 10.
Eleocharis engelmannii
Eleocharis cancellata
Robust plants known only from Missouri and described as Eleocharis engelmannii var. robusta have well-developed caudices, culms to 2 mm wide (pressed), spikelets to 2 cm, floral scales to 2.5 mm and slightly cartilaginous, styles mostly trifid, achenes to 1.5 × 1 mm, and tubercles 0.3–0.5 × 0.7–1 mm and to 2/5 as high as achene. Some specimens are intermediate between E. engelmannii and E. obtusa, or rarely with E. lanceolata. I have not seen specimens to verify literature reports of E. engelmannii from Manitoba, Connecticut, Delaware, Idaho, New Hampshire, North Carolina, Oregon, Rhode Island, South Carolina, South Dakota, or Vermont.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Of conservation concern.
Eleocharis cancellata is very similar to E. bella. The achenes of E. cancellata are relatively broader in relation to their length, the angles and ridges obscure and fewer, and the trabeculae very distinct and faintly wavy at 35X. R. McVaugh and W. R. Anderson (1974+, vol. 13) mentioned possible intermediates with E. acicularis from Mexico. Eleocharis cancellata has been reported from the flora area from three collections: (1) Texas, Jeff Davis County, A. Brant et al. 2237, 1993, originally identified as E. bella; (2) southwestern Texas or northern Mexico (probably from near San Antonio), Parry & Palmer 912, 1879–1880; and (3) Arizona, Santa Cruz County(?), C. Wright 1937, collected in 1851. Although it was also reported from New Mexico (H. K. Svenson 1929), E. cancellata probably does not occur there (R. McVaugh and W. R. Anderson 1974+, vol. 13).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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