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rhynchospore blanc, white beak-rush, white beaksedge

Thorne's beaksedge

Habit Plants perennial, densely cespitose, 6–75 cm; rhizomes mostly absent. Plants perennial, densely cespitose, 10–20 cm; rhizomes slender, short.
Culms

erect to curved, leafy, obscurely trigonous to nearly terete, few ribbed, slender.

lax, filiform, leafy.

Leaves

spreading to ascending, exceeding or exceeded by culm;

blades 0.2–0.3 mm wide, margins strongly involute or channeled, apex trigonous, tapering, setaceous.

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.

cluster of cymes 1–2, widely spaced, turbinate, sparse;

branches few; foliaceous bracts setaceous, longer than cymes.

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.

brown, lanceovoid to fusiform, 2.5–3 mm, apex acuminate;

fertile scales ovate, 1.5 mm, apex acute, midrib shortexcurrent.

Flowers

perianth bristles 10–12, slightly overtopping tubercle, retrorsely barbellate or rarely smooth, base often setose.

perianth absent.

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.

0.9–1 mm;

body lustrous pale brown, ellipsoidlenticular, 0.8–0.9 × 0.5–0.6 mm, margins narrow, wirelike;

surfaces minutely reticulate;

bristles 4–6, the longest from shorter than fruit midbody to fully as long, rarely reaching tubercle tip, minutely antrorsely barbellate;

tubercle shortconic, to 0.15 mm.

Principal

leaves mostly overtopped by culm;

blades narrowly linear to filiform, proximally flat, 0.5–1.5 mm, apex tapering, trigonous.

Rhynchospora alba

Rhynchospora thornei

Phenology Fruiting summer–fall. Fruiting late spring summer.
Habitat Acid, sphagnous, boggy, open sites, poor fens, often on floating mats or peaty interstices of rocky shores Fluctuating shores of limesink ponds, seeps over calcareous rock
Elevation 0–2000 m (0–6600 ft) 0–200 m (0–700 ft)
Distribution
from FNA
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
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; FL; GA; NC
[BONAP county map]
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.)

Of conservation concern.

Rhynchospora thornei, discovered by Robert Thorne from margins of a limesink pond in southwestern Georgia, has been extirpated at that site. Now the taxon is known from several Alabama and Florida locations and was recently found in eastern North Carolina by R. J. LeBlond.

Had S. Gale been sent material of Rhynchospora thornei at the time she was doing her excellent revision, she probably would have treated it as part of her series Rariflorae. Yet without its perianth bristles, R. thornei would be nearly identical to R. divergens and very similar to R. pusilla, both of which belong in subg. Psilocarya. Therefore, it forms an interesting link between subg. Rhynchospora (Eurhynchospora sensu Gale) and subg. Psilocarya.

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

Source FNA vol. 23, p. 214. FNA vol. 23, p. 221.
Parent taxa Cyperaceae > Rhynchospora Cyperaceae > Rhynchospora
Sibling taxa
R. baldwinii, R. brachychaeta, R. breviseta, R. caduca, R. californica, R. capillacea, R. capitellata, R. careyana, R. cephalantha, R. chalarocephala, R. chapmanii, R. ciliaris, R. colorata, R. compressa, R. corniculata, R. crinipes, R. curtissii, R. debilis, R. decurrens, R. divergens, R. elliottii, R. eximia, R. fascicularis, R. fernaldii, R. filifolia, R. floridensis, R. fusca, R. globularis, R. glomerata, R. gracilenta, R. grayi, R. harperi, R. harveyi, R. indianolensis, R. inexpansa, R. inundata, R. knieskernii, R. kunthii, R. latifolia, R. macra, R. macrostachya, R. megalocarpa, R. megaplumosa, R. microcarpa, R. microcephala, R. miliacea, R. mixta, R. nitens, R. nivea, R. odorata, R. oligantha, R. pallida, R. perplexa, R. pineticola, R. pleiantha, R. plumosa, R. punctata, R. pusilla, R. rariflora, R. recognita, R. scirpoides, R. solitaria, R. stenophylla, R. thornei, R. torreyana, R. tracyi, R. wrightiana
R. alba, R. baldwinii, R. brachychaeta, R. breviseta, R. caduca, R. californica, R. capillacea, R. capitellata, R. careyana, R. cephalantha, R. chalarocephala, R. chapmanii, R. ciliaris, R. colorata, R. compressa, R. corniculata, R. crinipes, R. curtissii, R. debilis, R. decurrens, R. divergens, R. elliottii, R. eximia, R. fascicularis, R. fernaldii, R. filifolia, R. floridensis, R. fusca, R. globularis, R. glomerata, R. gracilenta, R. grayi, R. harperi, R. harveyi, R. indianolensis, R. inexpansa, R. inundata, R. knieskernii, R. kunthii, R. latifolia, R. macra, R. macrostachya, R. megalocarpa, R. megaplumosa, R. microcarpa, R. microcephala, R. miliacea, R. mixta, R. nitens, R. nivea, R. odorata, R. oligantha, R. pallida, R. perplexa, R. pineticola, R. pleiantha, R. plumosa, R. punctata, R. pusilla, R. rariflora, R. recognita, R. scirpoides, R. solitaria, R. stenophylla, R. torreyana, R. tracyi, R. wrightiana
Synonyms Schoenus albus, Dichromena alba, Phaeocephalum album, R. luguillensis, Triodon albus
Name authority (Linnaeus) Vahl: Enum. Pl. 2: 236. (1805) Kral: Sida 7: 42, fig. 1. (1977)
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