Rhynchospora maguireana T.Koyama
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Authority
Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
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Family
Cyperaceae
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Scientific Name
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Description
Latin Diagnosis - E sectione Polycephalae subgeneris Haplostylis. Ex affinitate R. simplicis, a qua tamen valde recedit spiculis ellipsoideis brevioribus 4 vs 6 mm longis, squamis in-ferioribus apice pilosis, nuce obovatis, rostro conico tantum 1/2 mm vs 4 mm longo, inflorescentia conspicue paniculato-corymbosa, et capitulis turbinatis. Perennis dense caespitosa; rhizoma breve lignescens fibris brunneis rufo-brunneisve vestitus. Folia multa radicalia et superioria 1 vel 2 caulina; laminae anguste lineares 10-30 cm longae, 2-5 mm latae, 1-costatae, planiusculae, in sicco valde revolutae, tenuiter coriaceae, apice longissime acuminatae, praesertium ad marginem dense vel subdense longe pilosa, supra pilosae vel glabrescentes; vaginae 2-3 cm longae, rufo-brunneae, antice membranaceae cinnamomeae, dorso aut dense pilosae aut glabresentes. Culmi gracilescentes, 55-70 cm alti, 1.2-1.5 mm crassi, acute triquetri, 3- ad 5-nodosi, hirti vel subglabri, scabri vel sublaeves, internodiis 4-20 cm longis. Corymbi 2-4, remoti saepissime superiores 2 subapproximati, simplices, (1-) 2-4-capitulati; radii graciles vel subcapillares, longe exserti, inaequales, 1.5-9 cm longi, scaberuli, glabrescentes; bracteae foliaceae, laminis 1-2 mm latis corymbo suo paulo longioribus breviroribusve, vaginis 0.5-3 cm longis, pilosis vel glabrescentibus. Capitula inclinata ad suberecta, maturitate hemisphaerica vel turbinata, 8-10 mm in diametro, 4-6 mm alta, ferruginea, dense multi-(35-60)-spiculata. Bracteae involucrantes spiculas super-antes vel subaequantes; pars inferior oblonga vel ovato-oblonga, 1.5-2 mm longa, 1.21.5 mm lata, papillacea, ferruginea, margine fulvo-membranacea, ciliolata, apice subito contracta emarginatave; costa coriacea, 1-nervia, ex apice bracteae in aristam 3-5 mm longam scabridam excurrens. Spiculae sessiles, ellipticae vel ovato-ellipticae, 4-4.5 mm longae, 1.2-1.5 mm latae, subcompresso-teretes, 4-squamosae et 1-florae, ferrugineae vel rufobrunneae, apice basique acutae; bracteolae lanceolatae, 2 mm longae, membranaceae. Squamae subdistichae, membranaceae, rufo-brunneae; ima vacua, oblongo-obovata,2-2.5 mm longa, 1-nervia, apice acuta cum arista ca 1/2 mm longa pilosa; 2da vacua, elliptica, 2.5-3 mm longa, 1-1.2 mm lata, navicularis, apice acuta, coata sub-trinervia ex apice glumae in aristam rectem 1/2-3/5 mm longam dense pilosam excurrente; 3a florens, ovato-elliptica, valde navicularis, 3 mm longa, 1.2 mm lata, apice subacuta, mucronulata, glabra, costa subtrinervia non-aristata; 4a ovato-elliptica, vacua, 3.5-3.7 mm longa, 1.75-1.8 mm lata, apice subacuta vel acuta, mutica, costa tenuiter subtrinervia. Flos hermaphroditus, triander; anthera 1.5 mm longa. Setae hypogynae 0. Nux late obovata usque obovato-oribicularis, 1.4-1.6 mm longa, 1.25-1.3 mm lata, crasse biconvexa, basi cuneata, versus apicern rotundo-truncatam contracta, sub-conspicue marginata, facie laete brunnea vel glauco-brunnescens, subdense transversim undulata; stylus elongatus, gracilis, 6-7 mm longus, apice haud bifidus; stylopodium conicum, 0.4 mm longum, basi annulatum ad 1/2 mm latum, olivaceum.
Distribution and Ecology - Distribution. Known only by the cited specimens.
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Discussion
Fig 9.
Holotype. Frequent [in] wet places on rocks, 100 m alt, Río Atabapo, Río Orinoco, Amazonas, Venezuela. Bassett Maguire 29270 (NY). Paratypes. VENEZUELA. Amazonas: Río Orinoco, Caño Cupaven, right bank of Río Orinoco, opposite mouth of Río Atabapo, 125 m alt, locally abundant on laja margin, Wurdack & Adderley 42826 (NY). GUYANA. Watershed between Rupuruni and Kuyuwini Rivers, Parabaru Savanna, A. C. Smith 3065 (NY).
This distinct species is only remotely allied to R. simplex, from which it differs in its much shorter achene beaks and smaller spikelets in addition to the quite dissimilar superficial shape of the plant. Rhynchospora maguireana appears to be variable in the degree of pubescence on leaves and bracts, since in the holotype leaves and bracts are rather densely pilose, while in the other collection, Wurdack & Adderly 42826, such parts are nearly glabrous except on sparsely pilose margins of blades. Both specimens, however, exactly agree to one another in the floral details and I failed to recognize any taxonomic separation based on the pubescence.