Flora of North America species comparison

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Scleria

nutrush
Habit Herbs usually perennial, sometimes annual, cespitose or not, rhizomatous or not.
Culms

solitary or not, unbranched proximal to inflorescence, trigonous, (6–)10–100(–125) cm (high-climbing into trees), weak or wiry.
Leaves

few to many per culm, cauline, 3-ranked;

sheaths present;

ligules usually well developed, sometimes obsolete;

blades well developed (or rudimentary, sometimes absent on proximal leaves), shorter than, equaling, or overtopping culms, plane, keeled, or revolute, 0.5–9 mm wide, stiff, with prominent midvein, glabrous, scabrous, or pubescent.
Inflorescences

terminal, often axillary, sometimes pseudolateral, panicles, spikes, or 1 or more capitate or fasciculate clusters;

spikelets 1–100+;

bracts 1–3, ascending or erect, bristle-shaped, awl-shaped, or leaflike, sometimes appearing to be continuation of culm, 10–150 mm, shorter than or exceeding spikelets, glabrous or ciliate.
Spikelets

scales 3–10+, each subtending flower, distichous, proximal 2–4 scales empty, proximal fertile scale pistillate, distal fertile scales staminate or sometimes empty; occasionally some spikelets entirely pistillate or staminate.
Flowers

unisexual;

perianth absent;

stamens 1–3;

anthers 2–4 mm, apex usually mucronate or awned;

styles linear, 2–3-fid, base deciduous or persistent, hypogynium rudimentary or prominent, slender or enlarged.
Achenes

trigonous or rounded, 1–4 mm, smooth, tuberculate, verrucose, or reticulate, occasionally pubescent.

Scleria
Distribution
from USDA
Tropical and warm-temperate regions of both hemispheres
[BONAP county map]
Discussion

Species ca. 200 (14 in the flora).

Unusual structures provide important taxonomic markers in Scleria, necessitating some specialized terminology. The hypogynium is a peculiar, hardened disc at the base of the achene. In some species the hypogynium forms a prominent collar, while in others it is an inconspicuous ridge around the point of attachment of the achene. Before the achene abscises, the hypogynium is attached to a concave disc, the cupula, which remains with the inflorescence when the achene is shed. The contra-ligule (sometimes called the ligula) is a membranous flap on the rim of the leaf sheath on the opposite side from the blade. Contra-ligules are present in some other genera of Cyperaceae; their structure is seldom used taxonomically outside Scleria.

Scleria vaginata Steudel, native to Central and South America, was collected once as an adventive in southern Florida, where it is an aggressive vine over two meters. The hypogynium is well developed but lacks tubercles, and the achene is smooth, shining, and gray or purplish.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Hypogynium absent or vestigial, achene base tapered, indented or with small pits, appearing continuous with achene body in texture and color.
→ 2
1. Hypogynium present, appearing as basal zone differentiated from rest of achene by change in tissue appearance or physical border or gap or both.
→ 6
2. Achenes reticulate; plants annuals with weak bases, lacking rhizomes, with fibrous roots.
S. verticillata
2. Achenes essentially smooth; plants perennials with firm bases, with rhizomes.
→ 3
3. Inflorescences ± branched, spicate-paniculate; contra-ligules well developed, ciliate.
S. lithosperma
3. Inflorescences not obviously branched, headlike or spikelike; contra-ligules minute or absent.
→ 4
4. Inflorescence interruptedly spicate.
S. distans
4. Inflorescence a single cluster at summit of culm.
→ 5
5. Achenes 3–4 mm, base indented, without granulose pits.
S. baldwinii
5. Achenes 2–3 mm, base with 6 granulose pits.
S. georgiana
6. Leaves 10–25 mm wide; hypogynium bluntly 3-angled, smooth; main stem strongly retrorsely scabrous.
S. lacustris
6. Leaves 1–9 mm wide; hypogynium of lobes, papillose tubercles, or continuous papillose band; main stem ciliate or smooth.
→ 7
7. Hypogynium with narrow, smooth base proximal to 8–9 small, rounded, papillose tubercles.
S. oligantha
7. Hypogynium with 3 or 6 lobes or papillose tubercles or continuous and papillate with neither lobes nor distinct tubercles.
→ 8
8. Hypogynium continuous and without distinct lobes or tubercles, densely covered with whitish to brownish papillae; body of achene smooth.
→ 9
8. Hypogynium with 3 or 6 lobes or tubercles; body of achene usually reticulate or papillose.
→ 10
9. Leaves 3–9 mm wide; achenes 2–3 mm.
S. triglomerata
9. Leaves 1–2.5 mm wide; achenes 1.5–2 mm.
S. minor
10. Hypogynium with 3 oblong lobes; inflorescence paniculate, with visible branches.
→ 11
10. Hypogynium not distinctly 3-lobed, with 3 or 6 tubercles; inflorescence with spikelets in dense clusters, lacking obvious branches.
→ 12
11. Proximalmost lateral panicle spreading or drooping on filiform, flexuous peduncle (15–)20–100 mm; achene usually with tufts or lines of spreading, whitish or tawny hairs on ridges, rarely glabrous; distalmost lateral panicle with bract (including sheath) usually 1/4–3/4 length of terminal internode.
S. muehlenbergii
11. Proximalmost lateral panicle erect, sessile or on stiff, ± erect peduncle to 20(–90) mm; achene glabrous; distalmost lateral panicle with bract (including sheath) usually 3/4 or more length of terminal internode.
S. reticularis
12. Achenes reticulate-ridged.
S. curtissii
12. Achenes tuberculate, verrucose, or papillate, rarely nearly smooth.
→ 13
13. Hypogynium with 6 distinctly separate tubercles arranged in pairs; achenes 1–2.5 mm; leaves 1–2.5 mm wide.
S. pauciflora
13. Hypogynium with 3 tubercles (these often irregular or 2-lobed); achenes 2–3.5 mm; leaves 1–7 mm wide.
S. ciliata
Source FNA vol. 23, p. 242. Authors: A. A. Reznicek, John E. Fairey III, Alan T. Whittemore.
Parent taxa Cyperaceae
Subordinate taxa
S. baldwinii, S. ciliata, S. curtissii, S. distans, S. georgiana, S. lacustris, S. lithosperma, S. minor, S. muehlenbergii, S. oligantha, S. pauciflora, S. reticularis, S. triglomerata, S. verticillata
Name authority P. J. Bergius: Kongl. Vetensk. Acad. Handl. 26: 142, plates 4, 5. (1765)
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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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