Opercularia Gaertn.

Scientific Description

Common name. Stinkweeds. Family Rubiaceae.

Habit and leaf form. Shrubs (shrublets), or herbs. Herbs perennial. Young stems cylindrical (but grooved), or tetragonal (rarely). Self supporting, or climbing. Helophytic, or mesophytic, or xerophytic. Leaves opposite; petiolate to sessile; connate (via the stipules), or not connate; gland-dotted, or not gland-dotted; often foetid, or without marked odour; simple; epulvinate. Leaf blades entire; one-veined, or pinnately veined; cross-venulate. Leaves with stipules. Stipules interpetiolar (connate to the leaf base forming a sheath around the nodes, with 1–2 teeth per side); with colleters (secreting mucilage), or without colleters. Leaf blade margins entire, or serrate. Leaves without a persistent basal meristem. Domatia recorded, or not recorded; represented by pits, or pockets, or hair tufts. Stem anatomy. Nodes unilacunar, or tri-lacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite, or functionally male and functionally female, or hermaphrodite, functionally male, and functionally female. Unisexual flowers present, or absent. Plants hermaphrodite, or monoecious, or polygamomonoecious, or dioecious. Plants homostylous, or heterostylous. Entomophilous. Pollination mechanism conspicuously specialized (with passive pollen presentation involving stylar modification), or unspecialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. The terminal inflorescence unit cymose. Inflorescences terminal, or axillary (usually in a fork of a stem); a thyrse or dichasium with 2 to numerous flowers. Flowers small; regular; 3–5 merous; cyclic; tetracyclic. Free hypanthium present, or absent (depending on interpretation). Perianth with distinct calyx and corolla; 6–10; 2 -whorled; the two whorls isomerous. Calyx 3–5; 1 -whorled; polysepalous, or gamosepalous; lobed; open in bud; regular; persistent. Corolla 3–5; 1 -whorled; gamopetalous. Corolla lobes usually markedly shorter than the tube. Corolla valvate; tubular, or hypocrateriform; regular; deciduous. Fertile stamens present, or absent (when flower female). Androecium 4. Androecial members adnate (to the corolla tube); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4. Staminal insertion near the base of the corolla tube. Stamens becoming exserted; isomerous with the perianth; oppositisepalous; filantherous. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged. The anther appendages apical. Pollen shed in aggregates, or shed as single grains; if aggregated, in tetrads. Fertile gynoecium present, or absent (when flower male). Gynoecium 2 carpelled. The pistil 1 celled, or 2 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious to eu-syncarpous; inferior. Ovary unilocular, or plurilocular; 1 locular, or 2 locular. Gynoecium when bilocular transverse. Epigynous disk present. Gynoecium stylate. Styles 1; attenuate from the ovary, or from a depression at the top of the ovary; apical; shorter than the ovary at anthesis to much longer than the ovary at anthesis. Stigmas 1, or 2; wet type, or dry type; usually papillate; Group II type and Group IV type. Placentation when unilocular, parietal; when two or more locular, axile. Ovules in the single cavity when unilocular, 1; 1 per locule; ascending; anatropous, or hemianatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules septicidal, or loculicidal. Gynoecia of adjoining flowers combining to form a multiple fruit (flowers more or less connate at their base, together with their surrounding bracts forming a compound capsule dehiscing by abscission of the apical lid of each flower or several lids are more or less fused and shed as a single unit). Fruit 1 seeded, or 2 seeded. Seeds endospermic, or non-endospermic. Endosperm ruminate, or not ruminate; when present, oily. Seeds winged, or wingless. Cotyledons 2. Embryo straight, or curved. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Aluminium accumulation demonstrated, or not found.

Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania.

Etymology. From the Latin for "cover, lid"; refers to the opercula, or lid-like valves, on the fruit.