Trees or shrubs, evergreen, monoecious or dioecious. Ultimate branchlets cylindric, green, photosynthetic, slender, wiry, jointed with very short basal segments and one to numerous elongate segments; segments (internodes) striate with as many longitudinal ridges as leaves; ridges separated by furrows containing stomata. Leaves reduced, small, scaly, tooth-like in whorls of 4 to about 20, united at base forming many-toothed sheath at nodes, teeth corresponding to ridges on internode below. Stipules absent. Inflorescences spike-like or head-like (capitate) with alternating whorls of teeth-like bracts, within each bract a single flower, with 2 lateral scale-like bracteoles, usually persistent. Flowers sessile, unisexual. Male spikes catkin-like, usually terminal on lateral branches, short or elongate, terete, slender. Male Flowers: Tepals 1 or 2, scale-like, hooded, deciduous. Stamen 1; anthers large, bithecous, basifixed, dehiscence longitudinal. Female inflorescences head-like (capitate). Female Flowers: Perianth 0. Carpels 2, fused, only one carpel fertile, other usually +/- reduced or obsolete, ovary small, 1-locular, ovules usually 2, parietal, paired at base of ovary; style short with 2 long, red, filiform or linear stigmas. Infructescences +/- woody, cone-like with dense whorls of fruits, with 2 bracteoles of each flower enlarged as valves, persistent. Fruit a single-seeded flattened, terminally winged samara. Seed exalbuminous.

4 genera and 91 species

Casuarina equisitifolia