Tylophora R.Br.

Scientific Description

Family Asclepiadaceae.

Sometimes included in Apocynaceae. Subfamily Asclepiadoideae, Tribe Marsdenieae.

Habit and leaf form. Shrubs, or lianas; laticiferous (with clear, white (in T. cinerascens and T. williamsii) or yellow (in T. erecta and T. benthamii) latex). ‘Normal’ plants. Plants with roots (fibrous). Leaves cauline. To 1 m high (T. erecta). Climbing, or self supporting (T. erecta). Mesophytic. Leaves medium-sized; not fasciculate; opposite; not decurrent on the stems; not imbricate; petiolate, or sessile (rarely, though not in currently recognised Australian species). Petioles wingless. Leaves with ‘normal’ orientation; simple; epulvinate. Leaf blades dorsiventral; entire; flat; ovate, or obovate, or elliptic; pinnately veined; cross-venulate; cordate, or cuneate at the base, or rounded at the base (or truncate). Mature leaf blades adaxially glabrous; abaxially glabrous. Leaf blade margins entire; flat. Leaf anatomy. Hairs absent.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in umbels, or in racemes (with 1-many fascicles). Inflorescences simple; axillary. Flowers pedicellate; minute, or small; regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed. Corolla present; 5; 1 -whorled; appendiculate; gamopetalous; lobed; lobulate. Corolla lobes markedly longer than the tube. Corolla valvate, or imbricate (rarely); rotate; regular (to subrotate); variously coloured. Corolla members entire. Androecium present. Androecial members definite in number. Androecium 5. Androecial members adnate (epipetalous); united with the gynoecium (as a gynostegium); all equal; coherent (connate); 1 -whorled. Stamens 5; all more or less similar in shape (not markedly capitate); isomerous with the perianth. Filaments appendiculate (in a staminal gynostegial corona composed of 5 discrete lobes adnate to staminal column below, not overtopping anthers); connate into a tube, adnate to stigma. Anthers all alike; appendaged. The anther appendages apical. Pollen shed in aggregates; in tetrads. Gynoecium 2 carpelled. The pistil 2 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; synstylous; superior. Ovary plurilocular; 2 locular. Gynoecium stylate. Styles 2; partially joined (at the stylehead); apical. Stigmas 1; depressed-globose, not papillose. Placentation axile. Ovules 30–50 per locule (‘many’).

Fruit and seed features. Fruit 40–120 mm long; dehiscent; 1 locular (in 2 follicles, with one often aborting). Dispersal unit the seed. Seeds endospermic; compressed (ovate to oblong); conspicuously hairy (comose at micropylar end); with a tuft of hairs. Cotyledons 2.

Geography, cytology, number of species. Native of Australia, or adventive. Endemic to Australia, or not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, Queensland, New South Wales, and Victoria. Northern Botanical Province. A genus of over 75 species; 2 species in Western Australia; T. cinerascens (R.Br.) P.I.Forst., T. flexuosa R.Br.; 0 endemic to Western Australia.

Additional comments. From the Greek tylos (a knot) and phoros (bearing), referring to the shape of the staminal coronal lobes.

Additional characters Calyx with colleters (secreting mucilage) (at sinus bases). Annular corona absent. Corolline corona absent; adnate to gynostegium. Gynostegium markedly capitate. Gynostegial corona present (and staminal, and composed of 5 discrete lobes); consisting of lobes; staminal. Gynostegial staminal corona without a conspicuous hump; without an adaxial appendage. Corpusculum oblong. Caudicles not winged; not geniculate. Pollinia in the anther locule horizontal, or erect (almost); pellucid germinating mouth of pollinia absent. Pollen tetrads linear. Mature leaf blades bearing colleters (at lamina base), or lacking colleters (T. linearis).

Etymology. From the Greek for "callus, lump, knot" and "to bear"; refers to the pollen masses.