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Rhynchospora fusca

(Brown Beaksedge)

Common Names

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Common Names in English:

Brown Beaksedge

Common Names in French:

Rhynchospore Brun

Description

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Family Cyperaceae

Herbs, annual or perennial , cespitose or not, rhizomatous or not, stoloniferous or not. Roots fibrous , principally adventitious. Stems (culms ) usually trigonous , occasionally terete , rarely compressed , usually solid, rarely hollow or septate . Leaves basal and/or cauline, alternate, usually 3-ranked, rarely 2-ranked or multi-ranked, bases forming cylindric sheaths enclosing stem, margins usually fused; junction of sheaths and blades often with adaxial flaps of tissue or fringes of hair (ligules) ; blades frequently absent from some basal leaves , rarely from cauline leaves, when present divergent or ascending , flat, folded, plicate , rolled, or terete, linear , venation parallel. Primary inflorescences (spikelets ) a shortened axis; glumaceous bracts (scales ) 1-many, spirally arranged , sometimes 2-ranked, usually appressed or ascending; scales usually all fertile , each subtending a single flower, sometimes proximal and/or distal scales empty; lateral spikes often with basal, usually empty, usually 2-keeled scale (prophyll) ; occasionally prophyll subtending and enclosing rachilla, bearing 1 pistillate , sometimes (0-) 3 staminate flowers and empty scales (Carex, Cymophyllus, and Kobresia) . Secondary inflorescences panicles, often modified to corymb, pseudoumbel, cyme (anthela), raceme , spike, or capitulum (head ), rarely single spike, usually subtended by foliaceous or, less frequently, glumaceous bracts; secondary inflorescences sometimes simulating spikelets (Carex, Cymophyllus, and Kobresia) . Flowers hypogynous, bisexual in most genera, unisexual in Scleria, Carex, Cymophyllus, and Kobresia; perianth absent or with (1-) 3-6(-30) bristles and/or scales, usually falling off with fruit; stamens usually (1-) 3, rarely more, usually distinct ; anthers basifixed ; pistils 1, 2-3(-4) -carpellate, fused, locule 1; style undivided or branches 2-3(-4) ; stigma sometimes papillate . Fruits achenes, usually trigonous or biconvex ; pericarps thin (except in Scleria) . Seeds 1; testa thin, free from pericarp; embryo basal; endosperm abundant. x = 5-ca. 100.

Genera ca. 100, species ca. 5000 (27 genera, 843 species in the flora ) : worldwide.

No consensus exists regarding the number of genera and the overall relationships of genera within Cyperaceae. The most recent account of the family (P. Goetghebeur 1998) recognized 104 genera distributed among 4 subfamilies and 14 tribes . That arrangement differs somewhat from that of J. Bruhl (1995) . With one minor exception the arrangement of the family here follows that of Goetghebeur.

The family is characterized by the occurrence of a number of unusual cytological features including: (1) chromosomes with diffuse centromeres , (2) post-reductional meiosis, and (3) pollen grains formed from tetrads in which 3 of the 4 microspores fail to develop. The first two features are found in at least some Juncaceae and are unique to the two families. Juncaceae also have pollen in tetrads, but in that family all four microspores produce pollen grains. Some species in some genera of Cyperaceae (particularly Eleocharis) possess chromosomes with localized centromeres (S. S. Bir et al. 1993) . The wide range of chromosome numbers found in Cyperaceae is largely because of agmatoploidy; polyploidy has been hypothesized for some genera, especially Eleocharis, although polyploidy has not been demonstrated unequivocally.

Because of morphologic similarities in vegetative and inflorescence characters, the family has commonly been associated with Poaceae. Cytological features discussed above clearly indicate that to be a superficial similarity . Data from rbcL studies also support the view that Cyperaceae and Poaceae are not closely related (M. R. Duvall et al. 1993b; G. M. Plunkett et al. 1995) ; they do support the concept of close relationship between Cyperaceae and Juncaceae.

For most families of flowering plants the phenological data given are flowering times. Because most Cyperaceae cannot be reliably identified when in flower, in this volume fruiting time is given for all species by season , sometimes qualified by early, mid, or late, or by months. The fruiting time has been interpreted broadly to include the period when the fruit is more or less fully formed but not yet ripe . The fruiting period provided covers the entire range of the taxon . Quite a difference between fruiting periods in different parts of the range of the species may well occur, especially for widespread species and species with extensive elevation range.

For a recent, comprehensive review of the economic importance of Cyperaceae, see D. A. Simpson and C. A. Inglis (2001) .[1]

Genus Rhynchospora

Herbs, annual or perennial , cespitose or not, often scaly-rhizomatous. Culms procumbent to erect , usually trigonous , wiry to stout. Leaves basal and cauline, polystichous , mostly 3-ranked; sheaths open apically, glabrous ; ligules present or absent; blades flat, V-shaped in cross section or terete , typically keeled abaxially, margins involute or revolute , usually scabrid or scabridulous . Inflorescences terminal , rarely pseudolateral, paniculate , corymbose , anthelate , racemose, or capitate; spikelets 3-100 or more; involucral bracts 1-6, spreading or rarely the proximal erect, leaflike. Spikelets: scales spirally or distichously arranged, each subtending flower; 1 or more proximal scales empty. Flowers all bisexual or sometimes distalmost staminate ; perianth absent or of 2-12(-20) bristles , usually persistent in fruit, rarely deciduous, variously barbed or plumed, shorter or longer than achene, seldom smooth ; stamens 2-3; styles undivided or shallowly 2-fid, or deeply cleft into 2(-3) linear stigmatic branches; style base persistent as tubercle on fruit, usually articulate to achene apex, distinct , enlarged. Fruits achenes, borne on pedicellar joint , directly distal to compact , dilated receptacle; body various shades of brown, flattened, lenticular (biconvex ), or nearly terete, smooth and lustrous or variously ridged , pitted , alveolate (honeycombed ), cancellate (netted , latticed), papillate , or warty; tubercle mostly conic or variously triangular, terete or flattened and 2-edged, sometimes longitudinally sulcate , widest across base ; base along narrow transverse suture, lunate , 2-lobed, or topping achenial "neck" or buttress , much narrower, as wide as, or wider than achene apex, decurrent down achene margins.

Species over 250: worldwide, mostly in sunny places with wet, acidic soils.

The working basis for the classification used here is from G. Kükenthal, the first modern monographer of Rhynchospora worldwide (19491951). He divided the genus into two subgenera , Haplostylae (Nees) Bentham and Diplostylae Bentham, based on degree of stylar branching. In subg. Haplostylae the stylar apex is virtually unlobed, surmounted by two tubercle like stigmas, or shallowly bifid with the stigmatic branches rarely approaching 1 mm. Thus the stigmatic area is small compared to that of plants in subg. Diplostylae, in which the stylar apex is divided into two narrowly linear, elongate stigma branches.

Most members of Rhynchospora are cespitose. This does not preclude the possibility of some species (e.g. , R. caduca, R. mixta) from having well developed scaly rhizomes or others (e.g., R. oligantha, R. breviseta, R. rariflora, R. stenophylla) from forming dense, hard-based tufts from packed, intertwined short rhizomes. Only a few species are strongly clonal by elongate rhizomes; those are mostly in subg. Haplostylae (e.g., R. tracyi, R. careyana, R. inundata) or subg. Diplostylae sect. Dichromena (e.g., R. colorata).

Rhynchosporas are often dominant or co-dominant herbaceous graminoids in marshlands and savannas . Many species occuring in marshlands provide food for migratory waterfowl.[2]

Physical Description

Species Rhynchospora fusca

Plants perennial , cespitose, 10-50 cm; rhizomes stoloniferous , slender. Culms erect to excurved , filiform , leafy, ± terete . Leaves shorter than culm; blades ascending , filiform, proximally to 1.5(-2) mm wide, apex trigonous , tapering, setaceous . Inflorescences: lateral spikelet clusters (0-) 1-2, distant , terminal cluster ellipsoid to broadly turbinate or hemispheric , branches ascending; leafy bracts setaceous, overtopping clusters. Spikelets red-brown to deep brown, lanceoloid, (4-) 5-6(-7) mm, apex acute; fertile scales lanceolate, 4-5(-6) mm, apex acuminate, midrib often excurrent as awn . Flowers: bristles 5-6, longest reaching at least past tubercle base , mostly to tip or beyond, antrorsely barbellate . Fruits 2(-3) per spikelet, (2.3-) 2.5-2.6(-3) mm with pedicellar joint , receptacle, and tubercle; body lustrous , pale brown to deep brown, obovoid to ellipsoid , lenticular , 1-1.5 × 1 mm, margins narrow, flowing to tubercle; surfaces longitudinally finely lined , transversely very finely ridged with wavy rows of very narrow, vertical lattices, sometimes also with lines of shallow pits; tubercle triangular subulate , (0.7-) 1-1.3(-1.5) mm, base lunate, margins setulose proximally. Fruiting summer-fall. [source]

Habit: Graminoid

Habitat

Sands and peats of pond shores , bogs , and seeps ; 0-400 m [3].

Typically found at an altitude of 0 to 1,056 meters (0 to 3,465 feet).[4]

Biology

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Reproduction

Duration: Perennial

Taxonomy

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Unambiguous Synonyms

  1. Phaeocephalum fuscum (Linnaeus) House
  2. Rhynchospora Alba Fusca
  3. Rhynchospora alba (Linnaeus) Vahl Var. fusca (Linnaeus) Vahl
  4. Schoenus fuscus Linnaeus, Sp. Pl. Ed. 2, 2: 1664. 1763

Notes

Name Status: Accepted Name . Latest taxonomic scrutiny: 15-Mar-2000

Similar Species

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Members of the genus Rhynchospora

ZipcodeZoo has pages for 550 species, subspecies, varieties, forms, and cultivars in this genus. Here are just 100 of them:

R. aberrans · R. adulta · R. affinis · R. agostiniana · R. alba (White Beaksedge) · R. alba macra · R. alba var. macra · R. albescens · R. albiceps · R. albida · R. albo-marginata · R. albo-tuberculata · R. almensis · R. alpina · R. alta · R. amazonica · R. amazonica subsp. guianensis · R. andina · R. andresii · R. angolensis · R. angosturensis · R. angustipaniculata · R. arechavaletae · R. arenicola · R. argentea · R. aripoensis · R. aristata · R. aristata var. brevifoliata · R. aristata var. fuertesii · R. aristata var. suberecta · R. armerioides · R. armeroides · R. asperula · R. aurea · R. aureaeformis · R. axillaris · R. ayangannensis · R. bahamensis · R. baileyi · R. bakhuisensis · R. baldwinii (Baldwin's Beaksedge) · R. barbata · R. barrosiana · R. berteroi (Little Beaksedge) · R. beyrichii · R. biceps · R. biflora · R. biflora var. cryptantha · R. blauneri · R. blepharophora · R. bolivarana · R. boliviensis · R. boninensis · R. borinquensis · R. brachychaeta (West Indian Beaksedge) · R. brasiliensis · R. brevirostris · R. brevirostris var. truncata · R. breviseta (Shortbristle Beaksedge) · R. breviuscula · R. brittonii · R. brownii · R. bruneri · R. bucherorum · R. bulbosa · R. cabecarae · R. cacuminicola · R. caduca (Anglestem Beaksedge) · R. cajennensis · R. californica (California Beaksedge) · R. canaliculata · R. candida · R. capillacea (Needle Beaksedge) · R. capillacea var. leviseta · R. capillifolia · R. capitata · R. capitellata (Brownish Beaksedge) · R. capitellata f. controversa · R. capitellata var. controversa · R. caracasana · R. careyana (Broadfruit Horned Beaksedge) · R. cariciformis · R. carrillensis · R. castanea · R. caucana · R. cephalantha (Bunched Beaksedge) · R. cephalantha var. cephalantha (Bunched Beaksedge) · R. cephalantha var. typica · R. cephalophora · R. cephalotes · R. cephalotes var. comata · R. cephalotes var. imeriensis · R. cephalotoides · R. cernua · R. cernua var. depressa · R. chalarocephala (Loosehead Beaksedge) · R. chalarocephala Fern. & Gale var. angusta Gale · R. chalarocephala Fern. & Gale var. chalarocephala Fern. & Gale (Loosehead Beaksedge) · R. chalarocephala var. angusta (Loosehead Beaksedge) · R. chalarocephala var. chalarocephala (Loosehead Beaksedge)

More Info

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Further Reading

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Notes

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Contributors

Data Sources

Accessed through GBIF Data Portal December 10, 2007:

Identifiers

Footnotes

  1. Peter W. Ball, A. A. Reznicek, David F. Murray "Cyperaceae". in Flora of North America Vol. 23 Page 3, 4, 192, 243, 252. Oxford University Press. Online at EFloras.org. [back]
  2. Robert Kral "Rhynchospora". in Flora of North America Vol. 23 Page 6, 7, 200, 201, 231, 238. Oxford University Press. Online at EFloras.org. [back]
  3. "Rhynchospora". in Flora of North America Vol. 23 Page 206, 232, 233. Oxford University Press. Online at EFloras.org. [back]
  4. Mean = 158.590 meters (520.308 feet), Standard Deviation = 156.730 based on 3,306 observations. Altitude information for each observation from British Oceanographic Data Centre. [back]
Last Revised: 7/1/2009