Petrorhagia (Ser.) Link

Scientific Description

Family Caryophyllaceae.

Subfamily Caryophylloideae, Tribe Caryophylleae.

Habit and leaf form. Herbs; non-laticiferous and without coloured juice. ‘Normal’ plants. Leaves well developed. Plants with roots; non-succulent; unarmed. Annual, or perennial; to 0.5 m high. Self supporting. Mesophytic. Not heterophyllous. Leaves small, or medium-sized; not fasciculate; opposite; with blades (grasslike); sessile; simple; not peltate. Leaf blades entire; flat; linear (narrow, grasslike). Mature leaf blades adaxially glabrous, or scabrous; abaxially glabrous, or scabrous. Leaves without stipules. Leaf blade margins entire; flat. Leaf anatomy. Hairs present, or absent; glandular hairs absent.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries absent.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. Inflorescence many-flowered, or few-flowered. Flowers in cymes (paniculate to capitate). Inflorescences compound. The terminal inflorescence unit cymose. Inflorescences terminal. Flowers pedicellate; bracteate, or ebracteate; bracteolate, or ebracteolate; small; regular; tetracyclic. Floral receptacle with neither androphore nor gynophore (but sometimes developing an anthophore). Free hypanthium absent. Hypogynous disk present. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed. Calyx lobes markedly shorter than the tube. Calyx prominently 5–15 veined; glabrous; valvate; campanulate, or tubular (cylindrical). Epicalyx present, or absent. Corolla present; 5; 1 -whorled; polypetalous, or gamopetalous; dextrorsely contorted, or imbricate (rarely); white, or yellow, or pink, or purple. Petals clawed, or sessile. Corolla members deeply bifid, or entire. Androecium present. Fertile stamens present. Androecial members definite in number. Androecium 10. Androecial members all equal; coherent (more or less connate at the base); 2 -whorled. Androecium exclusively of fertile stamens. Stamens 10; diplostemonous (obdiplostemonous); oppositisepalous. Anthers separate from one another; dehiscing via longitudinal slits; introrse; bilocular; tetrasporangiate. Fertile gynoecium present. Gynoecium 1 carpelled. The pistil 1 celled. Gynoecium syncarpous; synovarious; superior. Ovary unilocular (but 4-locular at the base); 1 locular. Gynoecium stylate. Styles 2; free; simple. Stigmas 2; 1 - lobed. Placentation free central, or basal. Ovules campylotropous.

Fruit and seed features. Fruit dehiscent; a capsule. Dispersal unit the seed. Perisperm present. Seeds minute, or small.

Geography, cytology, number of species. Holarctic. Adventive. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania. 2n=26, 28, 30, 60. A genus of ca 28 species; 1 species in Western Australia; Petrorhagia velutina (Guss.) P.W.Ball & Heywood; 0 endemic to Western Australia.