Eleocharis robbinsii |
Eleocharis cancellata |
|
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Robbin's sppike-rush, Robbins' spikerush, Robbins' spikesedge, éléocharide Robbins |
Arizona spikerush |
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Habit | Plants perennial; rhizomes (0.5–)1–2 mm thick, longer internodes 2–3 cm, scales 5–7 mm; tubers sometimes present, apical, ovoid, 4–8 × 3–4 mm. | Plants annual(?), densely cespitose; rhizomes obscured among culm bases, delicate, internodes very short, scales not evident. |
Culms | acutely trigonous; spikelet-bearing culms 16–70 cm × 0.7–0.9 mm; when submersed plants often forming numerous, filiform, flaccid culms without spikelets, sometimes with whorls of slender branches, 0.1–0.3 mm wide; soft, sometimes septate-nodulose when aquatic, internally spongy, transverse septa incomplete. |
mostly ascending, terete or 4-angled, 2 cm × 0.2–0.3 mm, soft. |
Leaves | distal leaf sheaths persistent or decaying, membranous, apex obtuse to acuminate. |
distal leaf sheaths persistent, greenish to whitish, translucent, membranous, apex blunt. |
Spikelets | sometimes proliferous (when submerged), 9–33 × 1.5–3 mm; rachilla joints bearing prominent winglike remnants of floral scales; proximal scale with a flower, amplexicaulous, (5–)6–9.8 mm; floral scales 4–18, 0.5–1 per mm of rachilla, stramineous to pale brown, often minutely dotted reddish, without or rarely with darker submarginal band, narrowly ovate to lanceolate, 5–7.8 × 2–3 mm, thickly papery, membranous toward margins, apex narrowly rounded to acute. |
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. |
Flowers | perianth bristles 6–7, stramineous to reddish brown, proximally slightly flattened, subequal to equal, much exceeding to rarely shorter than achene, 3–5 mm, retrorsely spinulose; anthers yellow to reddish, 1.6–3.2 mm; styles 3-fid. |
perianth bristles absent; anthers orange-brown, 0.2–0.3 mm. |
Achenes | stramineous or medium brown, biconvex or compressed trigonous, narrowly obpyriform, 1.9–2.6 × 1–1.4 mm, adaxial face with 15–22 rows of rectangular, transversely elongated or nearly isodiametric cells, clearly sculptured at 10–15X, apex usually conspicuously constricted to short neck 0.4–0.7 mm wide, usually wider at tubercle base. |
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. |
Tubercles | stramineous to medium brown, high-pyramidal, 0.5–1.1 × 0.3–0.7 mm. |
grayish or brownish, often appressed, mostly pyramidal, 0.1 × 0.1 mm. |
Eleocharis robbinsii |
Eleocharis cancellata |
|
Phenology | Fruiting late spring–late fall. | Fruiting fall (Sep). |
Habitat | Shallow waters of fresh lakes and ponds with sandy-peaty soils | Wet springy places |
Elevation | 10–500 m (0–1600 ft) | 1700 m (5600 ft) |
Distribution |
AL; CT; DE; FL; GA; MA; ME; MI; MN; NC; NH; NJ; OH; SC; VA; WI; NB; NS; ON; QC
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TX; Mexico (San Luis Potosí) |
Discussion | I have not seen voucher specimens for literature reports of Eleocharis robbinsii from Indiana, Pennsylvania, or Rhode Island. Plants from South Carolina with the achene surface cells nearly isodiametric, the achene apex spongy, and the anthers to 3.2 mm may represent an undescribed taxon. (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.) |
Source | FNA vol. 23, p. 117. | FNA vol. 23, p. 111. |
Parent taxa | Cyperaceae > Eleocharis > subg. Limnochloa | Cyperaceae > Eleocharis > subg. Scirpidium |
Sibling taxa | ||
Name authority | Oakes: Mag. Hort. Bot. 7: 178. (1841) | S. Watson: Proc. Amer. Acad. Arts 18: 170. (1883) |
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