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The families of flowering plants.                                                                                                                                                                

Juncaceae Juss.

                        

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IncludingPrioniaceae, Sexglumaceae Dulac

Habit and leaf form. Herbs (mostly), or shrubs (a few with woody trunks, e.g. Prionium). Usually ‘normal’ plants. Leaves well developed, or much reduced, or absent (rarely). Annual, or perennial; with a basal aggregation of leaves (usually), or with neither basal nor terminal aggregations of leaves; when perennial rhizomatous, or tuberous. The shrubby forms pachycaul. Hydrophytic to mesophytic; the aquatics rooted. Leaves when hydrophytic submerged and emergent. Leaves evergreen; alternate; tristichous (nearly always), or distichous (e.g. Distichia); folded, or rolled, or terete, or flat; ‘herbaceous’, or leathery, or membranous (sometimes reduced to membranous sheaths); sessile; sheathing. Leaf sheaths with free margins, or with joined margins. Leaves with ‘normal’ orientation (except rarely and atypically in some Juncus species); simple; epulvinate. Lamina entire; acicular, or linear, or subulate, or setaceous; parallel-veined. Leaves ligulate (often, by coalescent apical auricles), or eligulate; stipulate (dubiously, in the form of hyaline lobes on the sides of sheaths), or exstipulate; with a persistent basal meristem, and basipetal development.

General anatomy. Plants without silica bodies. Accumulated starch exclusively ‘pteridophyte type’.

Leaf anatomy. Stomata present; paracytic. Guard-cells not ‘grass type’.

Lamina dorsiventral, or isobilateral, or centric. The mesophyll without calcium oxalate crystals (at least, no raphides). Minor leaf veins without phloem transfer cells (Juncus). Vessels present; end-walls simple, or scalariform and simple.

Stem anatomy. Young stems cylindrical. Secondary thickening absent. Xylem with vessels. Vessel end-walls simple, or scalariform and simple. Sieve-tube plastids P-type; type II.

Root anatomy. Root xylem with vessels; vessel end-walls scalariform and simple (mainly simple).

Reproductive type, pollination. Plants hermaphrodite (usually), or dioecious (rarely). Floral nectaries absent (nectaries lacking). Pollination anemophilous (usually), or entomophilous (rarely, or autogamous).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in heads, or in corymbs. The ultimate inflorescence unit cymose (usually monochasial). Inflorescences scapiflorous (often, more or less — the stems often extending only in relation to flowering), or not scapiflorous; terminal (but sometimes ‘pushed aside’ by an erect leafy bract, so as to appear lateral); panicles, corymbs or heads; spatheate (with one or more spathal bracts). Flowers bracteolate (usually with two prophylls), or ebracteolate; small; regular; (2–)3 merous; cyclic; tetracyclic, or pentacyclic. Perigone tube absent. Hypogynous disk absent.

Perianthof ‘tepals’; 3 (rarely), or 6; free; 1 whorled (rarely, the inner whorl absent), or 2 whorled (usually); usually isomerous; sepaloid, or petaloid; similar in the two whorls, or different in the two whorls (sometimes very different in size); green, or white, or brown, or purple, or black, or hyaline.

Androecium 6 (usually), or 2–3 (rarely). Androecial members free of the perianth; all equal; free of one another; 2 whorled (usually), or 1 whorled (rarely). Androecium exclusively of fertile stamens. Stamens 2–3, or 6 (usually); reduced in number relative to the adjacent perianth to diplostemonous. Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse, or latrorse; appendaged (sometimes, via the connective tip), or unappendaged. Endothecium developing fibrous thickenings. The endothecial thickenings spiral. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Pollen shed in aggregates; in tetrads. Pollen grains aperturate; 1 aperturate; ulcerate; 3-celled.

Gynoecium 3 carpelled. The pistil 1 celled, or 3 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary 1 locular, or 3 locular. The ‘odd’ carpel anterior. Gynoecium stylate (often shortly). Styles 1, or 3; free to partially joined; attenuate from the ovary; apical. Stigmas2 (brushlike); dry type; papillate; Group II type. Placentation when unilocular parietal, or basal (rarely — Luzula); axile. Ovules in the single cavity when unilocular 3 (Luzula), or 7–100 (usually ‘many’); 3–50 per locule (i.e. to ‘many’); ascending; non-arillate; anatropous; bitegmic; crassinucellate. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; small, ephemeral, or persistent. Synergids large. Endosperm formation helobial. Embryogeny onagrad.

Fruit non-fleshy; dehiscent (usually), or indehiscent (rarely); a capsule (usually), or capsular-indehiscent. Capsules usually loculicidal. Seedsendospermic. Endosperm not oily. Seeds with starch. Cotyledons 1. Embryo achlorophyllous (2/3); straight (small). Testa without phytomelan.

Seedling.Hypocotyl internode present (Luzula), or absent (Juncus). Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling cataphylls absent. First leaf centric (Juncus), or dorsiventral (Luzula). Primary root ephemeral.

Physiology, biochemistry. Cyanogenic (frequently), or not cyanogenic. Cynogenic constituents tyrosine-derived. Alkaloids absent (6 species). Proanthocyanidins present (e.g. Luzula, in trace amount), or absent (usually); when present, cyanidin. Flavonols present, or absent (Luzula); when present, quercetin. Ellagic acid absent. Saponins/sapogenins absent. C3. C3 physiology recorded directly in Juncus. Anatomy non-C4 type (Juncus).

Geography, cytology. Frigid zone to temperate. Arctic, North and South temperate and tropical mountains. Chromosomes with diffuse centromeres (Juncus, Luzula). X = (3-)6 or 20(-36).

Taxonomy.Subclass Monocotyledonae. Dahlgren et al. Superorder Commeliniflorae; Cyperales. APG 3 core angiosperms; Superorder Lilianae; commelinid Monocot; Order Poales.

Species 400. Genera 8; Andesia, Distichia, Juncus, Luzula, Marsippospermum,Oxychloë, Prionium, Rostkovia.

Economic uses, etc. A few species used locally for matting, chair seats, baskets, hats, etc.

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