Juncus

Juncus L., Sp. Pl. 1: 325. 1753 Type species. Juncus acutus L. References. Engelmann, Trans. Acad. Sci. St. Louis 2: 424-458. 1866, ibid. 2: 459-499. 1868; Buchenau, Bot. Jahrb. Syst.12: 167-461. 1890; Buchenau in Engler, Pflanzenreich IV, 36 (Heft 25): 98 226. 1906; Barros, Darwiniana 10: 358-460. 1953; Balslev, Fl. Ecuador 11: 4. 1979; Balslev, Fl. Neotropica 68: 69. 1996; Kirschner et al., Juncaceae. Species Plantarum: Flora of the World 7:1-336. 2002a; 8:1-192. 2002c. Annual or perennial, rhizomatous, glabrous herbs. Culms usually erect, rarely procumbent or ascending. Leaves alternate, scale like on the rhizomes, cataphyllous (i.e., with reduced blades) and/or foliar on the base of the culm, and bracteous in the inflorescence; sheaths open, usually conspicuously auriculate at the junction to the blade; blade linear with varying cross section, flat with raised margins and slightly channeled above, canaliculate, round to elliptic, or completely flat. Inflorescence compound and often decompound, cymose or racemose, often anthelate. Inflorescence bracts decreasing in size from the base of the inflorescence upwards, the lower bract often conspicuously different from the remaining ones. Flowers sometimes clasped by two bracteoles on the pedicel, bisexual. Tepals equal or subequal, lanceolate, entire, persistent, stramineous or castaneous, sometimes light green. Stamens three or six; filaments filiform or flat, sometimes widened at the base; anthers linear or oblong, obtuse. Gynoecium with sessile ovary; stigmas three, filiform, twining, papillose. Capsule 1-locular, 3-septate, or 3-locular. Seeds many, ellipsoid, oblong or ovoid, smooth, rugose or sometimes with reticulate pattern, brown, yellowish or castaneous. Etimology. The name Juncus is derived from the Latin verb “jungo” which means to join or unite, probably referring to ancient use of these plants for binding things together. Composition and distribution. Juncus is a cosmopolitan genus of about 315 species, most of which occur in the north temperate region, but with some proliferation in the temperate parts of the southern hemisphere. In the tropics the genus is absent in the lowlands but present at higher elevations, usually over 2000 meters above sea level. The Neotropical region has 41 species, tropical Africa has seven, and tropical Asia has four species of Juncus. In Colombia 18 species and three infraspecific taxa have been found.

KEY TO THE SPECIES OF JUNCUS IN COLOMBIA

1	Each flower clasped by two bracteoles, inserted on the pedicel just below the tepals in addition to the bract that supports the pedicel; inflorescence compound, cymose, with partial inflorescence often being repeatedly one sided or two-sided cymes branching in one plane (drepania or rhiphidia).	2
1'	Flowers without clasping bracteoles on the pedicel but with a floral bract at the base of the pedicel; inflorescence with the flowers grouped in flower heads which are arranged in an anthela	10
2	Leaf blades well developed, linear, flat or canaliculate; inflorescence terminal on the culm, lower inflorescence bract similar to cauline leaves	3
2'	Leaf blades lacking, leaves present as basally sheathing cataphylls only; inflores-cence psudolateral, lower inflorescence bract appearing as a continuation of the culm	8
3	Perennials with rhizome; inflorescence occupying 1/4 or less of total plant height; auricles present at the junction of the sheath to the blade	4
3'	Annuals without rhizome; inflorescence occupying half or more of total plant height; auricles absent	Juncus bufonius
4	Rhizome densely branching, not horizontally creeping, without filamentous cover of splitting leaf based, the culms arising in tufts.	5
4'	Rhizome horizontally creeping, covered with a filamentous layer of splitting leaf bases and cataphylls, the culms arising in dense rows on top of the rhizome.	6
5	Blades flat or channeled with even thickness over the cross section, adaxial surface with a band of hyaline cells occupying at least 3/4 of the width; auricles at the junction of the sheath to the blade membranous, white and scaríous, often elongate and longer than wide; inflorescence more or less lax and irregular, flowers in several loose, few flowered clusters with visible branch segments in between.	Juncus tenuis
5'	Blades terete, angled or channeled in cross section, when channeled then thicker in the central part of the cross section, adaxial surface with a band of hyaline cells occupying less than 1/3 of the width or lacking; auricles firm and cartilaginous, rounded and shorter than wide; inflorescence lax or congested.	Juncus dudleyi
6	Leaves terete or angled in cross section	7
6'	Leaf blades flat in cross section	Juncus cordobensis
7	Capsule equal to or longer than the tepals	Juncus imbricatus
7'	Capsule shorter than the tepals.	Juncus capillaceus
8	Pith aerenchymatous	9
8'	Pith parenchymatous	Juncus ramboi subsp. colombianus
9	Culms smooth	Juncus balticus subsp. andicola
9'	Culms ridged.	Juncus effusus
10	Leaf blades dorsiventrally flattened with the flat side towards the culm, not hollow.	Juncus cyperoides
10'	Leaves terete, hollow, septate by cross partitions that appear as nodules externally	11
11	Rhizome short creeping, long creeping, or densely branching	12
11'	Rhizome stoloniferous and/or ascending branching. Plants 1-10 cm tall; leaves 1-8 cm long; inflorescence of one or rarely two, 2-5-flowered heads; rhizome with a branching-ascending part	Juncus stipulatus
12	Plants not densely cespitose, rhizome creeping with short internodes; cataphylls present and usually conspicuous	13
12'	Plants cespitose, rhizome densely branching and not creeping; cataphylls absent or inconspicuous	15
13	Tepals acute, V-shaped in cross section, flexuose; capsule acuminate	Juncus liebmannii var. quitensis
13'	Tepals subulate, U-shaped in cross section, rigid; capsule beaked.	14
14	Flower heads stramineous; plants 65-135 cm tall; rhizome less than twice as thick as the culm; outer tepals usually longer than inner tepals and the capsule	Juncus densiflorus
14'	Flower heads castaneous; inflorescence 1-2 headed	Juncus echinocephalus
15	Plants less than 10 cm tall.	16
15'	Plants more than 10 cm tall	17
16	Rhizome densely branching; lower inflorescence bract much longer than the inflorescence.	Juncus breviculmis
16'	Rhizome branching-ascending.	Juncus stipulatus
17	Flower heads 2-3 flowered.	Juncus liebmannii var. quitensis
17'	Flower heads many-flowered.	18
18	Foliar leaves and lower inflorescence bract overtopping inflorescence	Juncus breviculmis
18'	Inflorescence overtopping foliar leaves and lower inflorescence bract.	19
19	Seeds 0.7-0.9 mm long; capsule 2.9-4.4 mm long.	Juncus ecuadoriensis
19'	Seeds less than 0.5 mm long; capsule less than 3.5 mm long; stamens six, rarely three.	20
20	Ultimate inflorescence branches >0.45 mm diameter, tepals rigid	Juncus pallescens
20'	Ultimate inflorescence branches <0.4 mm diameter, tepals soft.	Juncus microcephalus

Juncaceae
Juncus balticus
Juncus breviculmis
Juncus bufonius
Juncus capillaceus
Juncus cordobensis
Juncus cyperoides
Juncus densiflorus
Juncus dudleyi
Juncus echinocephalus
Juncus ecuadoriensis
Juncus effusus
Juncus imbricatus
Juncus microcephalus
Juncus pallescens
Juncus stipulatus
Juncus tenuis

Sin material de COL

Juncaceae