Common name. Pellitories. Family Urticaceae.
Habit and leaf form. Herbs. Annual, or perennial; plants with neither basal nor terminal concentrations of leaves. Mesophytic. Leaves small to large; alternate; spiral; petiolate; non-sheathing; simple. Leaf blades entire; flat; rhombic, or ovate; pinnately veined, or palmately veined; cross-venulate; cuneate at the base, or rounded at the base. Leaves without stipules. Leaf blade margins entire. Leaves without a persistent basal meristem. Leaf anatomy. Urticating hairs absent.
Reproductive type, pollination. Fertile flowers hermaphrodite and functionally male, or hermaphrodite, functionally male, and functionally female. Unisexual flowers present. Plants monoecious, or polygamomonoecious. Female flowers without staminodes. Male flowers with pistillodes. Anemophilous. Pollination mechanism conspicuously specialized (the filaments reflexing violently).
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes, or in fascicles (or clusters). The terminal inflorescence unit cymose. Inflorescences axillary; with involucral bracts (around lateral flowers). Flowers pedicellate, or sessile to subsessile; bracteate; minute, or small; regular; 3–4 merous. Hypogynous disk absent. Perianth sepaline; 3–4; 1 -whorled; joined; persistent, or deciduous; accrescent. Calyx present; (the perianth being thus interpreted) 3–4; 1 -whorled; gamosepalous; blunt-lobed; imbricate, or valvate; of female flowers tubular; regular; often green, or white; persistent; accrescent, or non-accrescent. Fertile stamens present, or absent (female flowers). Androecial members definite in number. Androecium 3–4. Androecial members free of the perianth; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 3–4; isomerous with the perianth; oppositisepalous; inflexed in bud (uncoiling elastically); filantherous. Anthers dorsifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium ostensibly 1 carpelled (i.e. with no obvious evidence of more than one carpel). The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium monomerous (ostensibly), or syncarpous (theoretically?); of one carpel (at least, usually with no evidence of syncarpy), or synstylovarious to eu-syncarpous (theoretically); superior. Carpel stylate; apically stigmatic; (if the gynoecium is considered monomerous) 1 ovuled. Placentation basal. Ovary unilocular; (if the gynoecium is considered pseudomonomerous) 1 locular. Gynoecium stylate. Placentation if recognised as syncarpous, basal. Ovules in the single cavity 1; funicled, or sessile; ascending; non-arillate; orthotropous to hemianatropous.
Fruit and seed features. Fruit non-fleshy. The fruiting carpel indehiscent; (if the gynoecium is considered monomerous) an achene. Fruit indehiscent; (if the gynoecium is considered syncarpous) achene-like; 1 seeded. Seeds scantily endospermic, or non-endospermic. Endosperm oily, or not oily. Cotyledons 2. Embryo straight.
Geography, cytology, number of species. World distribution: mainly in the Middle East with a few species in South America, Asia and Australia. Native of Australia and adventive. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, and Tasmania. Eremaean Botanical Province and South-West Botanical Province. A genus of 20 species; 3 species in Western Australia; 0 endemic to Western Australia.
Etymology. From the Latin for "wall"; some species grow on old walls.