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The families of flowering plants

L. Watson and M. J. Dallwitz

Juncaceae Juss.

Including Prioniaceae, Sexglumaceae Dulac

Habit and leaf form. Herbs (mostly), or shrubs (a few with woody trunks, e.g. Prionium). ‘Normal’ plants to switch-plants (mostly low herbs of cool, damp places, with a creeping sympodial rhizome which each year gives off a single, one-stemmed leafy shoot that elongates into a terminal inflorescence); often with the principal photosynthesizing function transferred to stems. Leaves well developed, or much reduced, or absent (usually narrow with large sheathing bases). Annual, or perennial (mostly); rhizomatous (mostly), or tuberous. The few shrubby forms pachycaul. Hydrophytic to mesophytic; the aquatics rooted. Leaves when hydrophytic submerged and emergent. Leaves alternate; tristichous (nearly always), or distichous (e.g. Distichia); folded, or rolled, or terete, or flat; variously ‘herbaceous’, or leathery, or membranous; sessile; sheathing (sometimes reduced to membranous sheaths). Leaf sheaths with free margins, or with joined margins. Leaves ‘normally orientated’ (usually), or borne edgewise to the stem (rarely and atypically in some Juncus species); simple; epulvinate. Lamina entire; variously acicular, or linear, or subulate, or setaceous (variously flat and grass-like, needle-like or centric); 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; leaf development ‘graminaceous’.

General anatomy. Plants without silica bodies.

Leaf anatomy. The leaf lamina dorsiventral, or bifacial, or centric. Stomata present; paracytic. Guard-cells not ‘grass type’. The mesophyll without crystals (at least, no raphides). Foliar vessels present; with simple end-wall perforations, or with scalariform end-walls and with simple end-wall perforations. Minor leaf veins without phloem transfer cells (Juncus).

Axial (stem, wood) anatomy. Young stems cylindrical. Secondary thickening absent.

The vessel end-walls simple, or scalariform and simple.

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 units cymose (usually monochasial). Inflorescences scapiflorous (usually, more or less — the one-jointed stems often extending only in relation to flowering), or not scapiflorous; morphologically terminal (but often in Juncus spp. ‘pushed aside’ by an erect leafy bract, and giving the appearance of being lateral on a leaf-like cylindrical stem); dense panicles, corymbs or heads, being usually crowded masses of cymes of some sort, these usually monochasial and often fan- or sickle-shaped; 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.

Perianth of ‘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. Stigmas 2 (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. Seeds endospermic. 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, phytochemistry. C3. C3 physiology recorded directly in Juncus. Anatomy non-C4 type (Juncus). Accumulated starch exclusively ‘pteridophyte type’. Cyanogenic (frequently), or not cyanogenic. Cynogenic constituents tyrosine-derived. Alkaloids absent (6 species). Saponins/sapogenins absent. 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. Sieve-tube plastids P-type; type II.

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.

General remarks. ‘Normal’ plants in the sense of exhibiting stems, roots, foliar organs and inflorescences, but as exemplified above, the vegetative morphology of this family is very difficult to encode for a satisfactorily worded natural language description!.

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

Illustrations. • Juncus australis and J. capillaceus: Hooker, Fl. Tasmaniae (1860). • Technical details: Luzula, Juncus. • Technical details: Prionium (Thonner). • Luzula, Juncus (B. Ent.).

Quotations

And be it moon, or sun, or what you please,
An if you call it a rush candle,
Henceforth I vow it shall be so for me
(‘Taming Of the Shrew’, iv., 5)

Will your answer serve to fit all questions?
. . . (As fit . . . ) as Tib’s rush for Tom’s forefinger
(‘All’s Well’, ii., 2 - alluding to a ‘scandalous’ medieval custom of pretending to marry with a ring made of rush)

Our gates,
Which yet seem shut, we have but pinned with rushes;
They’ll open of themselves
(‘Coriolanus’, i., 4)

She bids you
Upon the wanton rushes lay you down,
And rest your gentle head upon her lap
(‘1st Henry the Fourth’, iii., 1)

Let wantons, light of heart,
Tickle the senseless rushes with their heels
(‘Romeo and Juliet’, i., iv - alluding to the rush-covered floor of the dance-hall)


The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG).

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 22nd August 2016. delta-intkey.com’.

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