Monographs Details: Juncus arcticus subsp. mexicanus Balslev
Authority: Balslev, Henrik. 1996. Juncaceae. Fl. Neotrop. Monogr. 68: 1-167. (Published by NYBG Press)
Synonyms:Juncus compressus Jacq., Juncus complanatus Schult. & Schult.f., Juncus mexicanus Willd. ex Schult. & Schult.f., Juncus balticus var. mexicanus (Willd. ex Schult. & Schult.f.) Kuntze, Juncus orizabae Liebm., Juncus balticus var. crassiculmis Buchenau, Juncus crassiculmis (Buchenau) Herter, Juncus balticus var. columnaris Buchenau, Juncus balticus var. durangensis Buchenau
Description:Subspecies Description - Perennial herbs (5-) 15-30(-70) cm high. Rhizome creeping, 2-6 mm in diam., internodes very short or up to 2 cm long, the culms accordingly crowded or spaced, often with short side branches with short internodes giving rise to crowded culms. Culms 0.5-2 mm diam., laterally compressed, often twisted. Foliar leaves 1-2 to each culm, blades similar to the culm but often shorter. Inflorescence small, usually less than 20-flowered and less than 3 x 2 cm. Tepals 4-5.5 mm long, castaneous with green or grey midrib, becoming slightly shorter and stramineous at fruiting. Stamens 2-3 mm long with 1.5-1.8 mm long, linear anthers. Style 1-1.5 mm long. Stigmas 1.5-3 mm long. Capsule ellipsoid, apiculate, 3.5-4.5 mm long, slightly shorter than or as long as the tepals.

Discussion:The presence of foliar leaves in Juncus arcticus var. mexicanus is peculiar since the remainder of Juncus subgen. Juncus do not have foliar leaves. The blades are oval in x.s., laterally compressed but without sharp edges. They are linear with aerenchy-matous pith and may become as long as the culm. The presence of foliar leaves is a plesiomorphy in Juncus subgen. Juncus, which is otherwise distinguished from the related Juncus subgen. Poiophylli by the absence of foliar leaves (apomorphy).
Distribution:Mexico North America| Coahuila Mexico North America| Distrito Federal Mexico North America| Hidalgo Mexico North America| México Mexico North America| Morelos Mexico North America| Oaxaca Mexico North America| Puebla Mexico North America| San Luis Potosí Mexico North America| Tlaxcala Mexico North America| Veracruz Mexico North America| Zacatecas Mexico North America| Guatemala Central America| Quezaltenango Guatemala Central America| Totonicapán Guatemala Central America| Peru South America| Cusco Peru South America| Puno Peru South America| Bolivia South America| La Paz Bolivia South America| Chile South America| Atacama Chile South America|

Common Names:Caballoj muchon