Flora of North America species comparison

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Eleocharis tenuis

Eleocharis tuberculosa

dog's hair, slender spike-rush, slender spikesedge

cone-cup spikerush, long-tubercled spikerush, long-tubercled spikesedge
Habit 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. Plants perennial, forming dense clumps, not stoloniferous.
Rhizomes

present or not, caudexlike, ascending, 1 mm thick;

internodes and scales hidden by crowded culms, not evident.
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.

elliptic or sometimes circular, with several rounded ridges and sulcate when dry, 15–75 cm × 0.3(–1.5) mm, firm, minutely granular at 10X.
Leaves

distal leaf sheaths persistent, not splitting, proximally dark red (or yellow-brown), distally green or stramineous or red, membranous, apex often reddish, obtuse to acute, often callose, often with tooth to 0.2(–0.9) mm.

distal leaf sheaths persistent; stramineous to green, often minutely red-spotted, papery to membranous, apex subacute to narrowly acute, often with tooth-like callus.
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.

basal spikelets absent; never proliferous, ovoid, terete, 5–15 × 2.5–4 mm, apex acute;

proximal scale empty, deciduous, clasping 1/2 of culm, similar to floral scales;

subproximal scale often empty;

floral scales spiraled, 10–30, 5–6 per mm of rachilla, pale orange-brown, midribs green, broadly ovate, 2.5–4 × 1.5–2.5 mm, central area and often flanks papery to cartilaginous (or membranous), midrib evident, apex broadly rounded to obtuse.
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.

perianth bristles 5–6, bright brown, stout, slightly shorter than to equaling tubercle;

spinules rarely absent, dense, variably from divaricate to antrorse, very short, and blunt to acute, to often much longer and retrorse, sharply acute;

stamens 2–3;

anthers 0.5–1 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.

medium brown, obovoid to obpyriform, compressed (often obscurely) trigonous, angles evident, 0.9–1.7 × 0.8–2 mm;

apex often constricted proximal to tubercle, very coarsely cancellate at 10X, each face with 8–10 longitudinal rows of large depressions.
Tubercles

brown, pyramidal and to as high as wide to greatly depressed-apiculate, often rudimentary, 0.05–0.3 × 0.25–0.4 mm.

bone-white to pale orange-brown, often red-spotted, subpyramidal, cross section plano-convex, 0.9–1.7(–2.4) × 0.7–1.2–2(–2.2) mm, at least as high and wide as achene, spongy, apex rounded, often with an abaxial acute projection.

Eleocharis tenuis

Eleocharis tuberculosa
Phenology Fruiting spring (in south)–fall.
Habitat Wet soil, freshwater, ponds, lakeshores, streams, meadows, pine woods, grasslands, disturbed places, bogs
Elevation 0–500 m (0–1600 ft)
Distribution
from FNA
AL; AR; CA; CT; DC; DE; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MO; MS; NC; NE; NH; NJ; NY; OH; OK; PA; RI; SC; SD; TN; TX; VA; VT; WI; WV; NB; NS; PE; QC
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; FL; GA; LA; MA; MS; NC; NJ; SC; TN; TX; NS
[WildflowerSearch map]
[BONAP county map]
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).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Eleocharis tuberculosa evidently is closely related to E. tortilis, from which it differs in its larger tubercles, culms that are always elliptic in cross section, and perianth bristle spinules that are often divaricate to antrorse and often blunt. The specimens of E. tuberculosa from throughout its range which are like E. tortilis in having retrorsely spinulose perianth bristles have been named E. tuberculosa forma retrorsa Svenson (type from Massachusetts). Plants from Nova Scotia with nearly smooth bristles have been named E. tuberculosa var. pubnicoensis Fernald and E. tuberculosa forma pubnicoensis (Fernald) Svenson.

We have not seen voucher specimens for literature reports of Eleocharis tuberculosa from Connecticut, Delaware, Maine, Maryland, New Hampshire, New York, Pennsylvania, Rhode Island, or Virginia.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.
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.
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.
var. verrucosa
Source FNA vol. 23, p. 86. FNA vol. 23, p. 92.
Parent taxa Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Eleocharis Cyperaceae > Eleocharis > subg. Eleocharis > sect. Eleocharis > ser. Tenuissimae
Sibling taxa
E. acicularis, E. aestuum, E. albida, E. ambigens, E. atropurpurea, E. baldwinii, E. bella, E. bernardina, E. bicolor, E. bifida, E. bolanderi, E. brachycarpa, E. brittonii, E. cancellata, E. cellulosa, E. coloradoensis, E. compressa, E. cylindrica, E. decumbens, E. diandra, E. elliptica, E. elongata, E. engelmannii, E. equisetoides, E. erythropoda, E. fallax, E. flavescens, E. geniculata, E. intermedia, E. interstincta, E. kamtschatica, E. lanceolata, E. macrostachya, E. mamillata, E. melanocarpa, E. microcarpa, E. minima, E. montana, E. montevidensis, E. nana, E. nigrescens, E. nitida, E. obtusa, E. obtusetrigona, E. occulta, E. ovata, E. pachycarpa, E. palustris, E. parishii, E. parvula, E. quadrangulata, E. quinqueflora, E. radicans, E. ravenelii, E. retroflexa, E. reverchonii, E. robbinsii, E. rostellata, E. suksdorfiana, E. torticulmis, E. tortilis, E. tricostata, E. tuberculosa, E. uniglumis, E. vivipara, E. wolfii
E. acicularis, E. aestuum, E. albida, E. ambigens, E. atropurpurea, E. baldwinii, E. bella, E. bernardina, E. bicolor, E. bifida, E. bolanderi, E. brachycarpa, E. brittonii, E. cancellata, E. cellulosa, E. coloradoensis, E. compressa, E. cylindrica, E. decumbens, E. diandra, E. elliptica, E. elongata, E. engelmannii, E. equisetoides, E. erythropoda, E. fallax, E. flavescens, E. geniculata, E. intermedia, E. interstincta, E. kamtschatica, E. lanceolata, E. macrostachya, E. mamillata, E. melanocarpa, E. microcarpa, E. minima, E. montana, E. montevidensis, E. nana, E. nigrescens, E. nitida, E. obtusa, E. obtusetrigona, E. occulta, E. ovata, E. pachycarpa, E. palustris, E. parishii, E. parvula, E. quadrangulata, E. quinqueflora, E. radicans, E. ravenelii, E. retroflexa, E. reverchonii, E. robbinsii, E. rostellata, E. suksdorfiana, E. tenuis, E. torticulmis, E. tortilis, E. tricostata, E. uniglumis, E. vivipara, E. wolfii
Subordinate taxa
E. tenuis var. pseudoptera, E. tenuis var. tenuis, E. tenuis var. verrucosa
Synonyms Scirpus tenuis Scirpus tuberculosus, E. tuberculosa var. pubnicoensis
Name authority (Willdenow) Schultes: Mant. 2: 89. (1824) (Michaux) Roemer & Schultes: in J. J. Roemer et al., Syst. Veg. 2: 152. (1817)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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