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The families of flowering plants

L. Watson and M.J. Dallwitz

Macarthuriaceae Christenhusz

~ Molluginaceae

Habit and leaf form. Wiry or rush-like sub- shrubs, or trees. More or less ‘normal’ plants to switch-plants (the leaves sometimes all reduced to scales); with the principal photosynthesizing function transferred to stems (photosynthesizing mainly via the green stems). Leaves few, well developed to much reduced. Plants somewhat succulent to non-succulent. Rush-like, perennial (with somewhat succulent stems); with a basal aggregation of leaves to without conspicuous aggregations of leaves (the leaves when not all scale-like, progressively reduced to scales distally along the stems); rhizomatous (with woody underground stock). Xerophytic. Leaves persistent, or deciduous; minute to medium-sized; alternate; spiral; not terete; not fleshy, ‘herbaceous’, or membranous; petiolate to sessile; non-sheathing; simple. Lamina entire; linear (distally reducing along the stems); "obscurely veined". Leaves exstipulate. Lamina margins entire.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when solitary, axillary; when aggregated, in cymes (these compound). The ultimate inflorescence units cymose. Inflorescences terminal, or axillary; comprising "many-flowered, terminal or axillary compound cymes" with (1-)20 flowers. Flowers bracteate; minute to small; regular; cyclic; tetracyclic, or pentacyclic.

Perianth with distinct calyx and corolla, or sepaline; 5, or 10, or 15 (depending on number of sepals and presence or absence of corolla); joined (the sepals); 1 whorled, or 2 whorled, or 3 whorled; isomerous. Calyx 5, or 10; 2 whorled (the outer greener, the inner more scarious); basally gamosepalous. Calyx lobes markedly longer than the tube. Degree of gamosepaly (maximum length joined/total calyx length) slight. Calyx regular; imbricate. Corolla in M. australis, 5; 1 whorled; polypetalous; imbricate; regular; white, or pink; plain. Petals in M. australis, clawed; entire.

Androecium 8–10 (not always "8", if illustrations (q.v.) are reliable). Androecial members free of the perianth; all equal; basally coherent (into a cup); 1 adelphous; 1 whorled. Androecium exclusively of fertile stamens. Stamens 8–10 (cf. illustrations, but 8 according to Christenhusz et al.); when corolla present, both alternating with and opposite the corolla members; filantherous. Anthers basifixed; non-versatile; dehiscing via longitudinal slits (?); latrorse (?).

Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled, or 3 celled. Gynoecium syncarpous; synovarious to synstylovarious (with three stylodes fused basally into a single style, each with an unlobed stigma); superior. Ovary when not unilocular, 3 locular; sessile. Gynoecium stylate. Styles 3; free to partially joined (i.e., marginally, basally); from a depression at the top of the ovary; apical; shorter than the ovary. Stigmas 3; on the stylodes. Placentation 1–2(cf. illustrations of M. australis). Ovules in the single cavity when unilocular, 6–10 (?); 1–3(–4) per locule (?); arillate (the small aril becoming white, cupular).

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Dispersal unit the seed.

Physiology, phytochemistry. Anatomy probably non-C4 type (?). Betalains present (?).

Geography, cytology. Australian. Temperate and sub-tropical. SW and SE Australia. Australasia.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Caryophylliflorae; Caryophyllales. Cronquist’s Subclass Caryophyllidae; Caryophyllales. APG III core angiosperms; core eudicot; Superorder Caryophyllanae. APG IV Order Caryophyllales.

Species 4. Genera 1; Macarthuria.

General remarks. This inadequate draft description reflects the poor family description of Christenhusz et al. (who segregated it from Molluginaceae), supplemented from an Icones Plantarum illustration (q.v.) and Australian Floras. Floral morphological assignments of perianth members to calyx/corolla, stamen counts etc. in this circle of affinity (supposedly important in distinguishing APG-supported segregates from Molluginaceae s. lato) are unconvincing.

Illustrations. • Macarthuria australis: Hook. Ic. Pl. 5 (1842). • Macarthuria australis: Rye, in Flora of Perth Region 1 (1987). • floral diagrams of Macarthuria australis and M. apetala, with Limeum spp.: Engler, Bot. Jahrb 42 (1909).

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: 5th March 2018.’.