Habit and leaf form. Lianas, or herbaceous climbers. Leaves cauline. Stem internodes solid. Climbing; tendril climbers (tendrils axillary or on inflorescences, simple, up to 25 cm long). Mesophytic, or xerophytic. Leaves alternate; spiral; petiolate; non-sheathing; simple, or compound; when compound, palmate. Leaflets ovate, or orbicular. Leaf blades dissected, or entire (3–5 lobed); when simple, ovate, or orbicular; when dissected, palmately lobed; pinnately veined, or palmately veined; cross-venulate; auriculate at the base, or cordate (to acute). Leaves with stipules. Stipules free of one another; minute; caducous. Leaf blade margins entire. Leaves without a persistent basal meristem. Leaf anatomy. Hairs absent. Extra-floral nectaries present (2 glands on auricles at base of blade).
Reproductive type, pollination. Fertile flowers hermaphrodite, or functionally male, or functionally female, or functionally male and functionally female. Unisexual flowers present, or absent. Plants hermaphrodite, or monoecious (rarely), or dioecious (usually). Female flowers with staminodes. Male flowers with pistillodes. Entomophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes, or in racemes. The terminal inflorescence unit cymose. Inflorescences axillary; inflorescence few to many-flowered, pedunculate, with tendrils. Flowers pedicellate (flower borne on a stipe articulated with the pedicel); bracteate (minute, entire); ebracteolate; large; regular; 5 merous; cyclic. Floral receptacle developing an androphore, or with neither androphore nor gynophore; markedly hollowed, or not markedly hollowed. Free hypanthium present; campanulate to tubular; short. Hypogynous disk present (staminodial); of separate members. Perianth with distinct calyx and corolla; 5, or 6–16; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; polysepalous, or gamosepalous; blunt-lobed; imbricate; tubular (very similar to hypanthium); regular; persistent. Calyx lobes triangular. Corolla present; 5; 1 -whorled; appendiculate (with a conspicuous staminodal ‘corona’); polypetalous; imbricate; tubular to urceolate; regular; white, or cream (greenish-cream to white). Petals ovate. Fertile stamens present, or absent. Androecial members definite in number. Androecium 5. Androecial members free of the perianth; united with the gynoecium; all equal; coherent (connate towards base forming a staminal tube); 1 -whorled, or 2 -whorled, or 3 -whorled. Androecium including staminodes. Staminodes 15–50; petaloid, or non-petaloid, or petaloid and non-petaloid. Stamens 5; all more or less similar in shape; isomerous with the perianth; at base of calyx. Anthers basifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Fertile gynoecium present, or absent. Gynoecium (2–)3(–5) carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth to isomerous with the perianth. Gynoecium syncarpous; synovarious to eu-syncarpous; superior. Ovary unilocular; 1 locular; subsessile, or stipitate (gynophore). Gynoecium stylate. Styles 3 (usually); free to partially joined; apical. Stigmas 3. Placentation parietal. Ovules in the single cavity 20–50 (numerous); arillate; orthotropous to anatropous.
Fruit and seed features. Fruit fleshy, or non-fleshy (coriaceous to succulent); dehiscent; a capsule, or a berry; 1 celled; 10–60 seeded. Seeds endospermic. Endosperm ruminate, or not ruminate; oily. Embryo well differentiated. Cotyledons 2. Embryo straight.
Etymology. After Aden (place name), Arabia, the habitat of the original species.
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Western Australian Herbarium (1998–). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. https://florabase.dpaw.wa.gov.au/