Juncus acuminatus Michx.
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Authority
Balslev, Henrik. 1996. Juncaceae. Fl. Neotrop. Monogr. 68: 1-167. (Published by NYBG Press)
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Family
Juncaceae
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Scientific Name
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Type
Type. U.S.A. Carolina (holotype, P!).
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Synonyms
Juncus acuminatus var. legitimus Engelm.
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Description
Species Description - Perennial, cespitose herbs, 30-100 cm high. Rhizome densely branching, 2-4 mm diam., with thin inconspicuous scales. Culms clustered, erect, 1-3 mm diam., terete, smooth. Cataphylls 1-3 to each culm, to 10 cm long, green or reddish tinged, with distinct scariose margins. Foliar leaves 1-3 basal to each culm, to 30 cm long; sheath to 10 cm long, with scariose margins terminating in 2 rounded, 1.55 mm long auricles; blade 1-2 mm diam., terete, conspicuously septate. Inflorescence decompound, anthelate, (3-)5-15(-20) x 3-8 cm, flower heads 3-35, conical to globose, 5-10 mm diam., 10-40 flowered, stramineous, ultimate head bearing branches <0.4 mm diam. Lower inflorescence bract 1-5 cm long, much shorter than the inflorescence, with a reduced, terete blade, distal bracts shorter, floral bracts acuminate, to 3 mm long, scariose. Tepals 2.5-3.5 mm long, linear-lanceolate, acute to acuminate, outer tepals concave or V-shaped in x.s., inner tepals flat. Stamens 3, 1.5-2 mm long; filaments filiform; anthers oblong to linear, 0.5-0.7 mm long, shorter than the filaments. Capsule equalling the tepals, ovoid, trigonous, 3-3.5 x 0.9-1.3 mm, with ca. 0.3 mm long beak, light brown to stramineous, unilocular, the valves inflexing along the margins at maturity. Seeds oblong-ellipsoid, apiculate, 0.3-0.5 x 0.2-0.25 mm, reticulate, yellow-brown with hyaline outer seed coat.
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Discussion
Juncus acuminatus is similar to J. microcephalus in habit and may best be distinguished from it by having three stamens (vs. six) and a trigonous, acute (vs. round, acuminate) capsule. The two species are largely allopatric but overlap in Central America and S Mexico.
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Distribution
Juncus acuminatus is distributed throughout most of temperate North America from Maine to British Columbia, Georgia, and California, and in the Mexican and Central American highlands. It grows in swamps and at river banks at elevations of 1200-2200 m.
Mexico North America| Guanajuato Mexico North America| Guerrero Mexico North America| Hidalgo Mexico North America| Jalisco Mexico North America| México Mexico North America| Michoacán Mexico North America| Nayarit Mexico North America| Querétaro Mexico North America| San Luis Potosí Mexico North America| Veracruz Mexico North America| Guatemala Central America| Zacapa Guatemala Central America| Honduras Central America| Cortés Honduras Central America| Intibucá Honduras Central America| La Paz Honduras Central America| Morazán Honduras Central America| Ocotepeque Honduras Central America| Costa Rica South America| Alajuela Costa Rica Central America| Cuba South America|