Eleocharis tenuis

(Willdenow) Schultes

Mant. 2: 89. 1824.

Common names: Slender spike-rush dog’s hair
IllustratedEndemic
Basionym: Scirpus tenuis Willdenow Enum. Pl. 1: 76. 1809
Treatment appears in FNA Volume 23. Treatment on page 86. Mentioned on page 61, 65, 66, 67, 69, 85, 87, 88.

Plants perennial, mat-forming; rhizomes evident, 0.4–2 mm thick, soft to hard, cortex persistent, longer internodes 2–10 mm, scales persistent or decaying to fibers, 5–10 mm, papery, finely to coarsely fibrous. Culms terete or usually with 4 or 5 (–6) angles, often sulcate; 5–90 cm × 0.2–0.5 (–0.8) mm, firm to soft. Leaves: distal leaf-sheaths persistent, not splitting, proximally dark red (or yellowbrown), distally green or stramineous or red, membranous, apex often reddish, obtuse to acute, often callose, often with tooth to 0.2 (–0.9) mm. Spikelets ovoid, 3–6 × 1.5–2 mm, apex obtuse to acute; proximal scale amplexicaulous, apex entire; subproximal scale with flower; floral scales appressed in fruit, 20–60, 5–6 per mm of rachilla, medium to dark-brown, midrib region often paler, ovate, 1.5–2.5 × 1 mm, apex rounded (to acute), entire, rarely shallowly notched, carinate in distal part of spikelet. Flowers: perianth bristles absent or sometimes 1–3, stramineous to pale-brown, slender, to equaling achene, obscurely retrorsely spinulose; stamens 3; anthers brown, 0.8–1.8 mm; styles 3-fid. Achenes falling with or before scales, lemon yellow, dark yellow, medium brown, or green, obpyriform, trigonous, angles evident, sometimes prominent, 0.6–0.9 × 0.45–0.7 mm, finely to coarsely rugulose and usually alveolate (cancellate) at 10–20X, 6–10 (–14) sharp horizontal ridges in each vertical series. Tubercles brown, pyramidal and to as high as wide to greatly depressed-apiculate, often rudimentary, 0.05–0.3 × 0.25–0.4 mm.

Distribution

V23 119-distribution-map.jpg

N.B., N.S., P.E.I., Que., Ala., Ark., Calif., Conn., D.C., Del., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Mass., Md., Miss., Mo., N.C., N.H., N.J., N.Y., Nebr., Ohio, Okla., Pa., R.I., S.C., S.Dak., Tenn., Tex., Va., Vt., W.Va., Wis.

Discussion

Varieties 3 (3 in the flora).

The name Eleocharis capitata (Linneaus) R. Brown was long misapplied to E. tenuis (H. K. Svenson 1939). Although the extremes of the three varieties are very different, intermediates are fairly common. Some plants are intermediate with E. elliptica.

Eleocharis tenuis belongs to the E. tenuis complex, which comprises species 16–21 and is restricted to North America, where it is widely distributed except for the Southeast and Southwest. Eleocharis occulta, E. bifida, and E. nitida are very distinct, have little variation, and have relatively restricted ranges; E. tenuis, E. elliptica, and E. compressa are difficult to separate, are highly variable, and have relatively large ranges (see also discussions under E. compressa and E. elliptica). Eleocharis occulta and E. bifida are evidently closely related to E. compressa; they are known only from unglaciated areas south of the limits of Pleistocene glaciation, while E. compressa has a broad range in glaciated regions. The cytotaxonomic study by L. J. Harms (1972) of E. tenuis, E. elliptica, and E. compressa included artificial interspecific and infraspecific hybrids as discussed under those species.

Eleocharis tenuis var. pseudoptera might also be treated as E. elliptica var. pseudoptera following L. J. Harms (1972) because it is intermediate between E. tenuis var. tenuis and E. elliptica var. elliptica in most characters except for the 4-angled, usually deeply sulcate culms. It appears to intergrade with E. elliptica. It is placed in E. tenuis because many plants, including an isotype, are more like E. tenuis than E. elliptica; because most plants key more easily to E. tenuis; and to continue the use of the traditional name. The achenes of the holotype (from Lancaster county, Pennsylvania) and some other specimens closely resemble those of E. elliptica but are not obviously persistent after the scales fall. The usually diagnostic tooth on the distal leaf sheath in E. tenuis var. pseudoptera is also characteristic of E. elliptica var. elliptica; but in E. tenuis var. pseudoptera it is more often present and usually longer and stouter than in E. elliptica. The culms of the holotype of E. tenuis var. pseudoptera and many other specimens are 4- to 5-angled, and in some specimens are very irregularly to 6-angled and often rigid and compressed. L. J. Harms (1972) transferred E. tenuis var. pseudoptera to E. elliptica because he counted the same 2n = 38 chromosome number in both E. elliptica and E. tenuis var. pseudoptera and produced artificial E. elliptica × E. tenuis var. pseudoptera hybrids in which meiotic pairing and pollen stainability were very high. A. E. Schuyler (1977) reported 2n = 39 for E. tenuis var. pseudoptera as well as 2n = 34 and 68 for a putative E. tenuis var. tenuis × E. tenuis var. pseudoptera hybrid.

Putative hybrids between Eleocharis compressa and E. erythropoda of the E. palustris complex in Ontario have been reported (P. M. Catling and S. G. Hay 1993), and I have observed putative E. compressa × E. erythropoda and E. elliptica × E. erythropoda hybrids in the field in southeastern Wisconsin. It seems possible that introgression from E. erythropoda is responsible for some of the variation of both E. compressa and E. elliptica, especially the frequent presence of some 2-fid styles and lenticular achenes in both species and some (rarely all) entire floral scales in E. compressa (S. G. Smith 2001).

Selected References

None.

Key

1 Culms sharply angled, usually deeply sulcate, to 0.8 mm wide; some or all culms with distal leaf sheaths with stout apical tooth to 0.4–0.6(–0.9) mm; achenes usually lemon yellow to dark yellow, with 10–14 obscure to clearly evident depressions in each vertical series; tubercles mostly greatly depressed, much lower than wide. Eleocharis tenuis var. pseudoptera
1 Culms bluntly angled to smooth, seldom deeply sulcate, to 0.5 mm wide; distal leaf sheaths without tooth or with slender apical tooth to 0.2 mm; achenes usually yellow to green or brown, with 6–12 depressions in each vertical series; tubercles as high as wide to greatly depressed. > 2
2 Rhizomes 0.4–1 mm thick, longer internodes (2–)5–10 mm; tubercles as high as wide, sometimes greatly depressed; achenes finely rugulose and cancellate. Eleocharis tenuis var. tenuis
2 Rhizomes (1–)1.5–2 mm thick, longer internodes 2 mm; tubercles greatly depressed, rarely pyramidal; achenes coarsely (to finely) rugose at 10X and usually cancellate at 10–20X. Eleocharis tenuis var. verrucosa
... more about "Eleocharis tenuis"
greenish +, brown +, orange +  and yellow +
cancellate or reticulate +  and rugulose +
terete;trigonous;biconvex +
color +  and texture +
green +, brown +, medium +, dark yellow +  and lemon yellow +
0.06 cm0.6 mm <br />6.0e-4 m <br /> (0.09 cm0.9 mm <br />9.0e-4 m <br />) +
prominent +  and evident +
alveolate +  and rugulose +
0.45mm;0.7mm +
0.08 cm0.8 mm <br />8.0e-4 m <br /> (0.18 cm1.8 mm <br />0.0018 m <br />) +
S. Galen Smith* +, Jeremy J. Bruhl* +, M. Socorro González-Elizondo* +  and Francis J. Menapace* +
(Willdenow) Schultes +
flattened +
0 cm0 mm <br />0 m <br /> (6 cm60 mm <br />0.06 m <br />) +
shortened +
persistent +
enlarged +
Scirpus tenuis +
glumaceous +  and foliaceous +
2-ranked +  and arranged +
ascending +  and appressed +
parallel +  and divergent +
terete +, rolled +  and plicate +
Slender spike-rush +  and dog’s hair +
persistent +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.08 cm0.8 mm <br />8.0e-4 m <br />) +
5 cm50 mm <br />0.05 m <br /> (90 cm900 mm <br />0.9 m <br />) +
usually +  and terete +
firm;soft +
0.2mm;0.5mm +
red +, stramineous +, green +  and dark red +
N.B. +, N.S. +, P.E.I. +, Que. +, Ala. +, Ark. +, Calif. +, Conn. +, D.C. +, Del. +, Ga. +, Ill. +, Ind. +, Iowa +, Kans. +, Ky. +, La. +, Maine +, Mass. +, Md. +, Miss. +, Mo. +, N.C. +, N.H. +, N.J. +, N.Y. +, Nebr. +, Ohio +, Okla. +, Pa. +, R.I. +, S.C. +, S.Dak. +, Tenn. +, Tex. +, Va. +, Vt. +, W.Va. +  and Wis. +
membranous +  and thinly papery +
hypogynous +  and subtending +
biconvex +  and trigonous +
multi-ranked +, 2-ranked +, 3-ranked +  and alternate +
0.2 cm2 mm <br />0.002 m <br /> (1 cm10 mm <br />0.01 m <br />) +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
1 cm10 mm <br />0.01 m <br /> (?) +
flattened +
0 cm0 mm <br />0 m <br /> (6 cm60 mm <br />0.06 m <br />) +
with (1-)3-6(-30) bristles and/or scales +
2-3(-4)-carpellate +
3 (?) +  and 1 (?) +
stramineous;medium brown or red brown or blackish brown +
ascending +  and horizontal +
caudex-like +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
adventitious +
green +, brown +, medium +, dark yellow +  and lemon yellow +
decaying to fibers +  and persistent +
0.06 cm0.6 mm <br />6.0e-4 m <br /> (0.09 cm0.9 mm <br />9.0e-4 m <br />) +
basal +  and proximal +
prominent +  and evident +
rugulose +
trigonous;obpyriform +
0.5 cm5 mm <br />0.005 m <br /> (1 cm10 mm <br />0.01 m <br />) +
papery +  and finely coarsely fibrous +
0.45mm;0.7mm +
cylindric +
Illustrated +  and Endemic +
0.3 cm3 mm <br />0.003 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
1.5mm;2mm +
septate +, hollow +  and solid +
compressed +, terete +  and trigonous +
papillate +
Eleocharis +
Eleocharis tenuis +
Eleocharis (sect. Eleocharis) ser. Eleocharis +
species +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.09 cm0.9 mm <br />9.0e-4 m <br />) +
0 cm0 mm <br />0 m <br /> (0.02 cm0.2 mm <br />2.0e-4 m <br />) +
0.05mm;0.3mm +
pyramidal +
0.25mm +  and 0.4mm +
plant +  and mat-forming +