Habit and leaf form. Trees; deciduous. Leaves alternate; leathery; petiolate; simple. Leaf blades entire, or dissected (then 3–5-lobed); palmately veined. Leaves without stipules. Leaf anatomy. Hairs present, or absent.
Reproductive type, pollination. Fertile flowers hermaphrodite and functionally male. Unisexual flowers present. Plants andromonoecious (the male flowers more numerous). Male flowers with pistillodes (rudimentary ovary present).
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes, or in corymbs. Inflorescences terminal; dense, cymes corymbose. Flowers ebracteate (usually); regular. Perianth of ‘tepals’; 4–8; 1 -whorled; joined (basally); sepaloid; cream (in G. americanus). Androecial members markedly unequal (the staminodes shorter than the stamens). Androecium including staminodes (alternating with the fertile stamens). Stamens 4, or 5. Anthers dehiscing by longitudinal valves. Fertile gynoecium present, or absent (in male flowers). Gynoecium 1 carpelled. The pistil 1 celled. Carpels reduced in number relative to the perianth. Gynoecium monomerous; of one carpel; inferior. Carpel stylate; apically stigmatic (stigma capitate); 1 ovuled. Ovules pendulous.
Fruit and seed features. Fruit non-fleshy. The fruiting carpel indehiscent; samaroid (the nut ovoid or ellipsoid with 2 large membranous apical wings formed from the floral segments). Fruit 1 seeded.
Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, and Queensland. Northern Botanical Province.