Rhynchospora alba |
Rhynchospora gracilenta |
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rhynchospore blanc, white beak-rush, white beaksedge |
slender beaksedge |
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Habit | Plants perennial, densely cespitose, 6–75 cm; rhizomes mostly absent. | Plants perennial, densely cespitose or solitary, 10–100 cm; rhizomes absent. |
Culms | erect to curved, leafy, obscurely trigonous to nearly terete, few ribbed, slender. |
mostly lax, ascending to leaningexcurved, leafy, linear to filiform, terete. |
Leaves | shorter than culm; blades ascending, filiform to narrowly linear, proximally flat, 0.5–1.5(–2.5) mm wide, margins distally strongly involute, apex trigonous, tapering. |
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Inflorescences | clusters 1 or 2–3, then widely spaced, narrowly turbinate to hemispheric, 1.5–2.5 cm wide; subtending leafy bracts often exceeded by distal cluster. |
spikelet clusters 1–3(–4), proximalmost distant, dense to sparse, narrowly turbinate to hemispheric; peduncles and branches ascending; leafy bracts linearsetaceous, mostly overtopping clusters. |
Spikelets | pale brown to nearly white, ellipsoid, 3.5–5.5 mm, apex acute; fertile scales elliptic, 3–3.5(–4) mm, apex acute or acuminate, midrib excurrent as mucro. |
redbrown, ovoid to lanceoloid, (3.5–)4–5 mm, apex acute; fertile scales ovate, 3–4.5 mm, apex acute, mucronate to awnedcuspidate. |
Flowers | perianth bristles 10–12, slightly overtopping tubercle, retrorsely barbellate or rarely smooth, base often setose. |
bristles 6, mostly reaching tip of tubercle or beyond, antrorsely barbellate. |
Fruits | 1(–2) per spikelet, (2.3–)2.5–3 mm; body pale brown with paler center, stipitateobovoid, lenticular, 1.5–1.8(–2) × 0.9–1.2 mm; surfaces transversely striate, relatively smooth, rim narrow, flowing to tubercle base; tubercle narrowly triangularsubulate, 0.5–1.2 mm. |
1–3 per spikelet, (2.5–)3–3.5(–4.1) mm; body dark brown with small pale center, lenticular, broadly ellipsoid to suborbicular, 1.3–2.1 × 1.3–1.5 mm, smooth, margins narrow, flowing into tubercle; tubercle triangular-subulate, compressed, mostly 1.5–2 mm. |
Principal | leaves mostly overtopped by culm; blades narrowly linear to filiform, proximally flat, 0.5–1.5 mm, apex tapering, trigonous. |
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Rhynchospora alba |
Rhynchospora gracilenta |
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Phenology | Fruiting summer–fall. | Fruiting late spring–fall. |
Habitat | Acid, sphagnous, boggy, open sites, poor fens, often on floating mats or peaty interstices of rocky shores | Moist to wet sandy peaty substrates in ditches, bogs, seeps, wet savannas, barrens, and flatwoods |
Elevation | 0–2000 m (0–6600 ft) | 0–400 m (0–1300 ft) |
Distribution |
AK; CA; CT; DE; GA; ID; IL; IN; MA; MD; ME; MI; MN; NC; NH; NJ; NY; OH; OR; PA; RI; SC; TN; VA; VT; WA; WI; WV; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK; Fla(?); West Indies (Puerto Rico); South America(?); Eurasia
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AL; AR; DE; FL; GA; LA; MD; MS; NC; NJ; OK; PA; SC; TN; TX; VA; Central America; West Indies (Cuba)
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Discussion | The smooth-bristled Rhynchospora alba forma laeviseta Gale mostly occurs with the typical antrorsely barbellate type in Pennsylvania, the Great Lakes, British Columbia, Newfoundland, and Nova Scotia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Through the southern coastal plain are widerleaved examples of Rhynchospora gracilenta that are sparingly cespitose to solitary-stemmed, often with but a single terminal inflorescence with dense clusters of spikelets (var. diversifolia). That would be a tenable designation were it not for the large numbers of populations with intermediate habit. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 214. | FNA vol. 23, p. 236. |
Parent taxa | Cyperaceae > Rhynchospora | Cyperaceae > Rhynchospora |
Sibling taxa | ||
Synonyms | Schoenus albus, Dichromena alba, Phaeocephalum album, R. luguillensis, Triodon albus | Phaeocephalum gracilentum, R. drummondiana, R. gracilenta var. diversifolia, R. trichophylla |
Name authority | (Linnaeus) Vahl: Enum. Pl. 2: 236. (1805) | A. Gray: Ann. Lyceum Nat. Hist. New York 3: 216. (1835) |
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