Juncus imbricatus

Juncus imbricatus Laharpe, Essai Mongr. Jonc. 61. 1825. Syntypes: Argentina. “Buenos Aires”, P. Commerson s.n. (P); Chile. Concepcion, M. Lesson s.n. (K). Figs. 6, 12 Perennial cespitose herbs, 15-45 cm tall. Rhizome creeping, 2-3 mm diameter, covered with a filamentous dark brown layer of remaining sclerenchyma strands from splitting cataphylls and leaf bases; internodes very short and the culms arising in densely crowded rows. Culms erect, canaliculate, 0.5-1.5(-1.8) mm diameter. Cataphylls 3-4 to each culm, to 5 cm long, dark brown or upper ones sometimes yellow-brown or light green, with a rudimentary blade to 5 mm long. Blade bearing leaves all basal, 1-2 to each culm, 10-35 cm long; sheaths 1.5-6 cm long with membranous margins terminating in two 0.3-0.5 mm long auricles; blades filiform, 0.6-1 mm diameter, canaliculate and obtuse-angled, with an adaxial basal groove. Inflorescence terminal, compound, 1-30 flowered, consisting of (1-)2 4 clustered, unilateral cymes (drepania); lower inflorescence bract resembling a basal leaf, herbaceous, to 8 cm long and exceeding the inflorescence, or shorter than the inflorescence and needle-like, distal bracts progressively shorter, the ultimate ones membranous, to 3 mm long; each flower clasped by two 1.5-2 mm long bracteoles. Tepals unequal, lanceolate, midrib green, turning brown, margins castaneous, membranous at fruit ripening, outer ones 3.5-5 mm long, inner ones 3-4 mm long. Stamens six, 1.7-2.1 mm long; anthers linear, 0.8-1 mm long. Capsule ellipsoid, apically obtuse to truncate, trigonous with somewhat concave sides, 3.5-5 x 1.8-2.5 mm, castaneous, glossy at maturity, thick walled and not showing impressions of the contained seeds, 3-septate. Seeds broadly ovoid, asymmetrical, slightly apiculate, 0.4-0.6 x 0.2-0.3 mm, rugose, brown. Distribution and habitat. J. imbricatus occurs in the Andes from Colombia to N Argentina, in Concepcion in Chile, and in E South America in Corrientes in Argentina, in Uruguay, and in the highlands S of Buenos Aires. It also occurs in Mexico, South Africa, Australia, and Portugal, where it presumably is recently introduced since the plants are ruderal there. In the Andes it is as a weed on roadsides and in abandoned fields at elevations of 2300-3800 m above sea level. Together with J. capillaceus it is different from most other species of Juncus because it often grows and flowers in very dry habitats where the soil may be completely hardened. In Colombia this species is found in the center of the Cordillera Central (Valle del Cauca) and Cordillera Oriental (Boyacá and Cundinamarca), at elevations of 2300-2820 m. Comments. J. imbricatus is related to J. capillaceus, with which it shares the feature of a brush like cover of splitting leaf sheaths and cataphylls on the creeping rhizome. The two species are similar in several other respects, but are always distinct through the larger dimensions of J. imbricatus in both vegetative and reproductive structures, especially the size of the capsule (3.5-5 mm vs. 2.3-2.6 mm long). Representative specimens. Boyacá: Tunja, 2820 m, 23 Jul 1973, 23 Jul 1973, Ballesteros-G. 21, fr (COL). Cundinamarca: Guasca, 2300-2700 m, 10 Apr 1918, Brother AristeJoseph A141 fr (US), 3 Aug 1918, Brother Ariste-Joseph A364, fr (US); Bogotá, Universidad Nacional, 2600 m, 28-29 Apr 1986, Fernández-Alonso 6351, fr (COL); Zipaquira, catedral de sal, 2700 m, 2 Feb 1986, Fernández-Alonso 5076, fr (COL); municipios Suesca y Nemocón, hacienda Susatá, 2650 m, 23 Aug 2000, Fernández-Alonso 19081, (COL). Valle del Cauca: río Bugalagrande, Loma de Barragán, 2700 m, 13 Apr 1946, Cuatrecasas 20674A, fl (F, US). Locality unknow: San José, 9 Jul 1876, André 4025 (F).

Juncus

Jul 23
Fernández 5076

Juncaceae