Eleocharis robbinsii |
Eleocharis microcarpa |
|||||
---|---|---|---|---|---|---|
Robbin's sppike-rush, Robbins' spikerush, Robbins' spikesedge, éléocharide Robbins |
small-fruit spikesedge, smallfruit spikerush |
|||||
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 usually annual, tufted, sometimes mat-forming via proliferating and arching inflorescences (stoloniferous), sometimes entirely vegetative; rhizomes absent. | ||||
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. |
often ascending or arching, quadrangular or broadly elliptic, 2–40 cm × 0.1–0.4(–0.6) mm, soft. |
||||
Leaves | distal leaf sheaths persistent or decaying, membranous, apex obtuse to acuminate. |
distal leaf sheaths persistent or disintegrating, pale brown, green or red-brown, streaked or mottled red-brown or purple, translucent, membranous, apex narrowly acute. |
||||
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. |
basal spikelets absent; often proliferous, ovoid to ellipsoid or lanceoloid, terete, 2–10.7 × 1–2 mm, apex acute; proximal scale empty, persistent, amplexicaulous, dissimilar to floral scales, often longer, often resembling an involucral bract, ovate to lanceolate, midrib markedly thickened and broad and often prolonged beyond lamina; subproximal scale with flower; floral scales spiraled, colorless, whitish, or pale brown, streaked or mottled red-brown or purple, midribs green and red-brown or green and purple, ovate to elliptic, 0.8–1.5 × 0.4–0.8 mm, membranous, midrib obscure to prominent. |
||||
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 present or sometimes apparently absent; stamens 3; anthers 0.15–0.35; styles 3-fid. |
||||
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. |
whitish to olive or pale brown, sometimes spotted olive or red-brown, obovoid, trigonous (or subterete), angles prominent, 0.55–0.8 × 0.3–0.5 mm, apex constricted proximal to tubercle, smooth. |
||||
Tubercles | stramineous to medium brown, high-pyramidal, 0.5–1.1 × 0.3–0.7 mm. |
green or pale brown to red-brown, trigonous. |
||||
Eleocharis robbinsii |
Eleocharis microcarpa |
|||||
Phenology | Fruiting late spring–late fall. | |||||
Habitat | Shallow waters of fresh lakes and ponds with sandy-peaty soils | |||||
Elevation | 10–500 m (0–1600 ft) | |||||
Distribution |
AL; CT; DE; FL; GA; MA; ME; MI; MN; NC; NH; NJ; OH; SC; VA; WI; NB; NS; ON; QC
|
AL; FL; GA; IN; LA; MA; MD; MI; MS; NC; NJ; PA; SC; TN; TX; VA; West Indies
|
||||
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.) |
Varieties 2 (2 in the flora). Specimens of Eleocharis brittonii and E. microcarpa without achenes are often difficult to distinguish. More detailed study of the four apparent entities across the two species is warranted. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
||||
Key |
|
|||||
Source | FNA vol. 23, p. 117. | FNA vol. 23, p. 95. | ||||
Parent taxa | Cyperaceae > Eleocharis > subg. Limnochloa | Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Tenuissimae | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Name authority | Oakes: Mag. Hort. Bot. 7: 178. (1841) | Torrey: Ann. Lyceum Nat. Hist. New York 3: 312. (1836) | ||||
Web links |