[irn: 13825]

  • Authority

    Balslev, Henrik. 1996. Juncaceae. Fl. Neotrop. Monogr. 68: 1-167. (Published by NYBG Press)

  • Family

    Juncaceae

  • Scientific Name

    Juncus arcticus Willd.

  • Type

    Type. Norway. Without collector and number (B-W 6865!, 2 sheets).

  • Description

    Species Description - Perennial herbs, 20-170 cm high. Rhizome creeping, 2.5-10 mm diam., branching but with long unbranched segments, internodes very short or more often up to 4 cm long, the insertion of the culms accordingly crowded or spaced, sometimes with a creeping part with long internodes and side branches with short internodes. Culms erect, 1-7 mm diam., smooth or slightly wrinkled to striate, but only very rarely with longitudinal ridges. Cataphylls 2-3 to each culm, lower one 1-8 cm long, distal one 3-25 cm long, usually mucronate by a = 3 mm long, acicular, rudimentary blade, yellow to light brown or stramineous. Foliar leaves absent or, in var. mexicanus, present and then 1-2 to each culm, the blade terete, laterally compressed, very short to equalling the culm. Inflorescence pseudolateral, few- to many-flowered, usually lax and then up to 15 x 7 cm, sometimes congested and only 2.5 x 2 cm, compound, cymose, consisting of several congested cymes, of which the ultimate ones are unilateral drepania. Lower inflorescence bract appearing as a continuation of the culm, (2-)5-15(-25) cm long, or usually constituting between 1/10 and 1/5 (sometimes less) of the total plant height, distal bracts progressively shorter, scariose. Each flower clasped by two 1.5-2.5 mm long, acute, scariose bracteoles. Tepals equal or outer ones longer, lanceolate, stramineous to dark brown or castaneous, sometimes lighter colored along the midrib and at least the inner ones often with scariose margins, outer tepals 3-5.5 mm long, concave, acuminate, inner tepals 3-5 mm long, flat to concave, acute. Stamens 6, 1.5-3 mm long; filaments flat, widened toward the base; anthers linear 0.7-2.5 mm long, 1-6 x the length of the filaments. Style 0.5-1.5 mm. Stigmas 1.5-3 mm. Capsule ellipsoid to ovoid, apiculate, round to trigonous or slightly 3-lobed, 2.5-4.5 x 1.5-2 mm, light to dark brown, often light-colored at the base and dark at the apex, glossy, 3-septate. Seeds ellipsoid, oblong, ovoid, or irregularly shaped, short apiculate, 0.6-0.8 x 0.2-0.5 mm, rugose, light brown to castaneous below a hyaline outer seed coat.

  • Discussion

    Buchenau (1906) treated Juncus arcticus sensu stricto, J. lesueurii Bolander (type from Pacific North America), and J. andicola Hooker (type from Ecuador) of the Junci genuini laevis complex as three geographically restricted species. In addition to these three species, populations representing a wide array of morphological variation, and distributed over the range of the complex, were treated as 11 varieties of J. balticus Willdenow.

    In Buchenau’s (1906) treatment, the neotropical populations were classified as J. lesueurii, J. andicola, and J. balticus with four varieties. In our current, much expanded, collections, I have not found any basis for dividing this complex into distinct species. There is, however, a strong geographically correlated variation that I treat as three varieties of J. arcticus, which is the oldest species name for the complex.

  • Distribution

    In a broad circumscription, as here applied, Juncus arcticus is circumboreal and extends to the south through the Rocky Mountains in W North America, the Mexican Sierra Madres, and in the Andes from Colombia to Patagonia.

    Mexico North America| United States of America North America| Colombia South America| Ecuador South America| Peru South America| Bolivia South America| Argentina South America| Chile South America|