Common name. Sidas. Family Malvaceae.
Habit and leaf form. Shrubs, or herbs (usually with a stellate indumentum or glabrescent). Plants unarmed. Annual, or perennial; to 0.2–2 m high. Mesophytic, or xerophytic. Not heterophyllous. Leaves medium-sized; alternate; spiral; petiolate; non-sheathing; simple. Leaf blades dorsiventral; entire, or dissected (rarely and shallowly); ovate, or obovate, or oblong (or linear-oblong), or orbicular; more or less pinnately veined, or palmately veined; cordate, or rounded at the base. Mature leaf blades adaxially pubescent; abaxially pubescent. Leaves with stipules (stipules filiform, linear or subulate). Stipules often persistent, or caducous (rarely). Leaf blade margins mostly serrate, or crenate, or entire (rarely). Leaf anatomy. Hairs present; complex hairs present. Complex hairs stellate. Extra-floral nectaries absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.
Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’ (due to the reduction or abortion of the upper leaves); axillary; short in racemes, or in panicles, or in spikes. Inflorescences terminal, or axillary; inflorescence of solitary flowers, axillary clusters or short racemes, more rarely of terminal or axillary spikes. Flowers pedicellate (pedicels articulate in the upper half); small; regular; 5 merous; tetracyclic. Hypogynous disk absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present (sometimes with 10 basal ribs); 5; 1 -whorled; gamosepalous; lobed; lobulate (5-lobed); erect, or spreading; hairy; valvate; exceeded by the corolla; regular; persistent; accrescent, or non-accrescent. Calyx lobes ovate, or triangular. Epicalyx absent. Corolla present; 5; 1 -whorled; polypetalous (adnate to the base of the staminal column); contorted; hairy abaxially; hairy adaxially, or glabrous adaxially; plain, or with contrasting markings; yellow, or orange, or white (sometimes). Petals obovate. Androecium present. Androecial members indefinite in number. Androecium 50–100 (i.e. ‘many’). Androecial members adnate; all equal; coherent (connate; the filaments fused in a column surrounding the style); 1 - adelphous (the tube attached to the petals); 1 -whorled. Androecium exclusively of fertile stamens (or rather, half-stamens, each having only a half anther). Stamens 50–100. Anthers dehiscing via longitudinal slits; introrse; unilocular. Gynoecium 5–14 carpelled (in a single whorl). The pistil 5–14 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 5–14 locular. Gynoecium stylate. Styles 1; more than 4-branched (5–14-branched, i.e. as many as the carpels); apical. Stigmas 5–14; capitate (or truncate). Placentation axile. Ovules 1 per locule.
Fruit and seed features. Fruit 3–20 mm long; non-fleshy; hairy, or not hairy; a schizocarp (discoid, separating septicidally into indehiscent or 2-valved mericarps and leaving a persistent central axis). Mericarps 5–12. Dispersal unit the mericarp (laterally compressed, more or less trigonous, apex sometimes produced into 2 awns). Seeds 1 per mericarp (reniform in outline). Seeds basically not conspicuously hairy, or conspicuously hairy (the hilum may be shortly hairy).
Geography, cytology, number of species. World distribution: America and warmer regions of both hemispheres. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, and Australian Capital Territory. Northern Botanical Province and South-West Botanical Province. 1n = 7 for S. angutissima, S. regnellii and S. variegata; n = 14 for S. lindheimeri. A genus of c. 200 species; 37 species in Western Australia.
Additional comments. Sida is now considered to be a greatly reduced genus with 4 species in W.A., i.e. only those with a 10-ribbed calyx (Fryxell 1987) and the rest probably belong to Sidastrum or some other genera.
Etymology. From the Greek for "pomegranate or water lily".