(Subfamily Byttnerioideae), Tribe Hermannieae.
Habit and leaf form. Shrubs; evergreen; non-laticiferous and without coloured juice. ‘Normal’ plants. Leaves well developed. Plants with roots; non-succulent. Leaves cauline. To 0.3 m high. Self supporting, or climbing; scrambling (‘prostrate’). Mesophytic. Not heterophyllous. Leaves small; alternate; with blades; petiolate (shortly); with ‘normal’ orientation; simple; not peltate. Leaf blades neither inverted nor twisted through 90 degrees; dorsiventral; entire; flat; ovate, or obovate, or elliptic; pinnately veined. Mature leaf blades adaxially glabrous; abaxially pubescent (sparsely stellate hairy). Leaves with stipules. Stipules leafy (green); persistent, or caducous (on the oldest parts). Leaf blade margins serrate, or crenate; flat. Leaf anatomy. Hairs present; complex hairs present. Complex hairs stellate.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous.
Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; not crowded at the stem bases; axillary. Inflorescence few-flowered. Inflorescences simple (when present); axillary. Flowers pedicellate; bracteate. Bracts 1 deciduous. Flowers small; regular; not resupinate; neither papilionaceous or pseudo-papilionaceous; 5 merous; cyclic; tetracyclic. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present (‘non-petaloid’); 5; 1 -whorled; gamosepalous; lobed. Calyx lobes about the same length as the tube. Calyx hairy (margins ciliate), or glabrous; more or less equalling the corolla; campanulate; regular; neither appendaged nor spurred. Epicalyx absent. Corolla present; 5; 1 -whorled; polypetalous; regular; stellate hairy abaxially; stellate hairy adaxially; white to purple. Petals elliptic, or oblong. Androecium present. Fertile stamens present. Androecial members definite in number. Androecium 5. Androecial members free of the perianth; free of the gynoecium; markedly unequal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5; all more or less similar in shape; isomerous with the perianth; alternisepalous; all opposite the corolla members; filantherous. Filaments filiform. Anthers all alike; introrse; bilocular. Fertile gynoecium present. Gynoecium 5 carpelled. The pistil 5 celled. Carpels isomerous with the perianth. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 5 locular; sessile. Gynoecium stylate. Styles 1 (short); apical. Stigmas 1; minutely 5 - lobed. Placentation axile.
Fruit and seed features. Fruit ca 6 mm long; stellate hairy; dehiscent; a capsule. Capsules loculicidal. Fruit 5 celled. Dispersal unit the seed. Fruit 50 seeded. Seeds several.
Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, and New South Wales. Eremaean Botanical Province. A genus of 1 species; 1 species in Western Australia; G. biniflora F.Muell. (Western tar-vine); 0 endemic to Western Australia.
Additional comments. Named after Ernest Giles, leader of the exploring expedition of 1875.