Juncus L.
Sp.Pl. 2:325 (1753)

Name Status: Current
Browse to the list of specimens for Juncus L.

Scientific Description
H.R. Coleman, Thursday 8 September 2016

Family Juncaceae.

Habit and leaf form. Herbs; evergreen. Perennial, or annual (occasionally). Leaves basal (mostly). Plants with a basal concentration of leaves (usually), or with neither basal nor terminal concentrations of leaves. Young stems cylindrical. When perennial rhizomatous. Helophytic to mesophytic. Heterophyllous (leaf forms include scale-like on the rhizomes, cataphyllous (i.e. with reduced blade), foliar at the base of the culm and bracteous in the inflorescence). Leaves alternate; tristichous; sessile; sheathing. Leaf sheaths with free margins. Leaves with ‘normal’ orientation (except rarely and atypically in some Juncus species); simple; epulvinate. Leaf blades entire; flat, or rolled (channelled), or solid; when ‘solid’ terete; linear; parallel-veined. Leaves ligulate, or eligulate; without stipules; with a persistent basal meristem, and basipetal development. Vegetative anatomy. Plants without silica bodies. Leaf anatomy. Guard-cells not ‘grass type’. Hairs absent. Stem anatomy. Secondary thickening absent.

Reproductive type, pollination. Fertile flowers hermaphrodite (usually), or functionally male, or functionally female. Unisexual flowers present (rarely), or absent. Plants hermaphrodite (usually, protogynous), or dioecious (rarely). Floral nectaries absent (nectaries lacking). Anemophilous, or entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes. The terminal inflorescence unit cymose (usually monochasial). Inflorescences scapiflorous; terminal (but sometimes ‘pushed aside’ by an erect leafy bract, so as to appear lateral); the cymes contracted into clusters or expanded into panicles; spatheate (with one or more spathal bracts). Flowers bracteolate (usually with two prophylls), or ebracteolate; small; regular; 3 merous; cyclic; tetracyclic, or pentacyclic. Perigone tube absent. Hypogynous disk absent. Perianth of ‘tepals’; 6; 2 -whorled; isomerous; free; sepaloid; similar in the two whorls, or different in the two whorls (the tepals of the outer whorl usually slightly longer and more rigid, with narrower membranous margins than those of the inner whorl); yellow, or red to brown, or green. Fertile stamens present, or absent (rarely, when flowers female). Androecium 3, or 6. Androecial members free of the perianth; all equal; free of one another; 1 -whorled, or 2 -whorled. Androecium exclusively of fertile stamens. Stamens 3, or 6; isomerous with the perianth, or diplostemonous. Filaments filiform or flat. Anthers linear or oblong; basifixed; non-versatile; dehiscing via longitudinal slits; introrse, or latrorse; four locular; unappendaged. Pollen shed in aggregates; in tetrads. Fertile gynoecium present, or absent (rarely flowers male). Gynoecium 3 carpelled. The pistil 3 celled, or 1 celled (then partially 3-celled). Gynoecium syncarpous; synstylovarious; superior. Ovary unilocular, or plurilocular; 1 locular, or 3 locular. The ‘odd’ carpel anterior. Ovary sessile. Gynoecium stylate (often shortly). Styles 1; attenuate from the ovary; apical. Stigmas 3; dry type; papillate; Group II type. Placentation when unilocular parietal; axile, or parietal. Ovules in the single cavity when unilocular 20–100 (i.e. ‘many’); 20–50 per locule (i.e. ‘many’); ascending; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit 1 locular (although 3-septate), or 3 locular; 20–120 seeded. Seeds ellipsoid, oblong or ovoid, often shortly apiculate or appendaged at one or both ends; endospermic. Endosperm not oily. Seeds non-arillate; with starch. Cotyledons 1. Embryo straight (small). Seedling. Hypocotyl internode present, or absent. Mesocotyl absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling cataphylls absent. First leaf centric, or dorsiventral. Primary root ephemeral.

Physiology, biochemistry. Photosynthetic pathway: C3.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania. Eremaean Botanical Province and South-West Botanical Province.

Additional characters Stigmas the stigmatic area globose (twining).

Taxonomic Literature

  • Wheeler, Judy; Marchant, Neville; Lewington, Margaret; Graham, Lorraine (2002). Flora of the south west, Bunbury, Augusta, Denmark. Volume 1, introduction, keys, ferns to monocotyledons. Australian Biological Resources Study. Canberra.
  • Harden, Gwen J. (1993). Flora of New South Wales. Volume 4. New South Wales University Press. Kensington, N.S.W.