Juncus trifidus L.
Juncaceae, rush family.
Sp. Pl. ed 1: 326. 1753.
Plants caespitose; forming dense tufts from a matted creeping horizontal stem; less than 15 cm high, or more than 15 cm high; 10–20(–30) cm high. Ground-level or under-ground stems horizontal; rhizomatous (rhizomes with numerous yellowish-brown and somewhat lustrous, fibrous sheaths 1–3 cm long); compact. Aerial stems erect (stiff and wiry); circular or oval in cross-section; glabrous. Leaves mostly basal (occasionally cauline); alternate; deciduous (blades), or marcescent (sheaths). Petioles absent. Sheaths with the margins fused to the apex. Ligules absent. Blades 20–75(–100) mm long; 0.4–0.8 mm wide (filiform); straight; linear; with blade auricles (lacerate, 2–3 mm long); flat, or caniculate (fleshy); with parallel veins; adaxial surface glabrous. Blades abaxial surface glabrous. Leaf apices acuminate.
Flowering stems with leaves; glabrous. Leaf or reduced bract closely associated with the base of the inflorescence present; conspicuous and leaf-like (usually 2 or 3 leaves that extend well beyond the inflorescence). Flowers solitary (rarely), or in inflorescences (usually). Inflorescences cymose, or head-like; inflorescence dense; inflorescence 0–0.6 cm long. Flowers per inflorescence 1–5; small, less than 5 mm in diameter or length; sessile or subsessile. Floral bracts apex entire. Perianth present. Calyx sepals 3; free; brown; scarious; glabrous. Petals 3; free; brown (and scarious); lanceolate; unlobed; 2–5 mm long; same length as the calyx (or slightly shorter). Stamens 6. Anthers 1–1.2(–1.5) mm long. Carpels syncarpous; 3. Gynoecia superior. Styles completely fused. Styles 1. Stigmas per style 3. Ovules 15–25. Fruit with calyx persisting; a capsule; elongate-cylindrical (with a pointed top); not distinctly flattened; dehiscent; 2.5–3.5 mm long; 1–1.5 mm wide; sessile; dry; brown. Seeds 15–25; 1–1.4 mm long (irregular and variable in form with attenuate membranous structures at both ends); brown (yellowish); smooth.
Chromosome information. 2n = 30.
Distribution. Amphi-Atlantic. Low arctic. Range in the Canadian Arctic Archipelago limited. Uncommon. Arctic Islands: Baffin.
Ecology and habitat. Substrates, slopes; on seepage slopes, dry; gravel, sand. Occurs on springy or sandy slopes on Baffin Island. In the Beekman Peninsula, the plant is found in sheltered sandy sites, often in iron-rich sands.
Notes. Polunin (1940) considered this species a "southern" type, apparently eking out a rather precarious existence and sometimes only 5 or 6 cm high, although more often attaining a height of some 15 cm. Marchand and Roach (1980), in a study of reproductive strategies of pioneering alpine species, reported that in the White Mountains of New Hamsphire J. trifidus appeared capable of sexual reproduction. Successful invasion of disturbed sites, however, was probably restricted to fairly local areas where there is a high fallout of seed.
Illustrations. • Herbarium sheet. Plant with long leaves associated with the inflorescence. Collected by Père Arthème Dutilly, Aug 27, 1936 from Nunavut, Baffin Island, Kimmirut. CAN 10119. • Close-up of inflorescence. Right: Plant in flower with conspicuous stigmas (st) and auricles at the base of the leaf (au). Note the bracteoles (br) subtending the flowers. Above: Mature capsule with pointed top (pt). • Arctic Island distribution.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L.Consaul, R.L. Boles, R. Elven and M.E. LeBlanc. 2001 onwards. Flora of the Canadian Arctic Archipelago. Volume 1. Pteridophytes and Monocotyledons: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 16th March 2001. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Aiken, Dallwitz et al. (1999) should also be cited (see References).
