| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Anarthriaceae Cutler & Airy Shaw

~ Restionaceae-Anarthrioideae.

Habit and leaf form. Rushlike herbs (A. prolifera with the stems many-branched and curling below the inflorescences, unbranched in the other species). ‘Normal’ plants, or switch-plants (as exemplified by A. prolifera being vegetatively hard to interpret, the long basal leaves not apparent in the mature clumps, the flattened stems and peduncles leaflike, subtended by spathes and bracts which range from leaflike with folded laminae to reduced to their sheaths); with the principal photosynthesizing function transferred to stems (and peduncles, in A. prolifera). Leaves well developed, or much reduced, or absent (depending on interpretation of the material examined). Perennial; without conspicuous aggregations of leaves (the genuine leaves when present mostly basal, but not rosetted); 0.2–0.6 m high; rhizomatous. Ambiguously helophytic to mesophytic (usually in winter-wet depressions or swampy ground, though of xerophytic appearance). Leaves and bracts alternate; distichous; tapered to points, flat (at least with definite upper and lower surfaces in some species), or folded, or terete; sheathing. Leaf sheaths not tubular. Leaves with blades borne edgewise to the stem to with blades ‘normally orientated’; simple. Lamina entire; acicular to lanceolate. Leaf development presumably ‘graminaceous’.

General anatomy. Plants without silica bodies. Chlorenchyma including ‘peg cells’.

Leaf anatomy. Stomata present; paracytic. Guard-cells ‘grass type’ (grasslike). The mesophyll with sclerenchymatous idioblasts; without crystals. Foliar vessels present.

Axial (stem, wood) anatomy. Secondary thickening absent.

The vessel end-walls scalariform.

Reproductive type, pollination. Unisexual flowers present (usually). Plants monoecious (rarely), or andromonoecious, or gynomonoecious, or dioecious (usually). Female flowers with staminodes, or without staminodes. Gynoecium of male flowers absent. Floral nectaries absent (? — no septal nectaries). Pollination anemophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in panicles; in ‘spikelets’ (the chaffy bracteoles and longer perianth lending the small flowers a spikelet-ike aspect). Inflorescences narrow and spikelike, or lax paniculate cymes; spatheate (with leaflike spathes). Flowers bracteate; bi- bracteolate (the unequal bracteoles much shorter than the perianth); regular; 3 merous; cyclic. Perigone tube absent.

Perianth of ‘tepals’; 6; free; 2 whorled; isomerous; sepaloid; similar in the two whorls (glume- or bract-like, folded).

Androecium 3. Androecial members free of the perianth; free of one another, or coherent; when coherent, 1 adelphous (the filaments connate); 1 whorled. Androecium exclusively of fertile stamens. Stamens in male flowers, 3 (exserted); isomerous with the perianth; oppositiperianthial. Anthers basifixed; latrorse; bilocular; tetrasporangiate. The endothecial thickenings girdling. Pollen grains aperturate; 1 aperturate; ulcerate. The ulcus without an operculum; with an annulus. Interapertural exine scrobiculate. Interapertural interstitium columellate. Pollen grains 3-celled.

Gynoecium 3 carpelled. The pistil 3 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 3 locular. Gynoecium non-stylate. Styles 3; free (elongated). Stigmas 3 (the styles stigmatic almost throughout). Placentation apical. Ovules 1 per locule; pendulous; orthotropous; bitegmic; tenuinucellate. Embryo-sac development Polygonum-type. Synergids non-haustorial. Hypostase present (near the chalazal end).

Fruit non-fleshy; indehiscent; a nut. Seeds endospermic (the endosperm mealy). Seeds with starch. Testa without phytomelan.

Physiology, phytochemistry. Flavonols present; quercetin, or kaempferol and quercetin (kaempferol in infloresences).

Geography, cytology. Temperate. South West Australia.

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

Species 5. Genera 1; Anarthria.

General remarks. This description, prepared with reference only to Anarthria, needs revising if latter-day proposals to transfer the S.W. Australian monotypics Hopkinsia and Lyginia from Restionaceae be accepted.

Illustrations. • Anarthria prolifera: habit (photo). • Anarthria prolifera: spikelets (photo). • Anarthria prolifera: habitat (photo). • Anarthria scabra: Hutchinson. • Anarthria scabra and A. gracilis, leaf anatomy: Arber, Bot. Gaz. 74 (1922).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or 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). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 8th June 2026. delta-intkey.com’.

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