Xanthorrhoea Sm.

Scientific Description

Family Xanthorrhoeaceae.

Habit and leaf form. Shrubs, or ‘arborescent’ (the habit characteristic, the trunk up to 2 m, or almost acaulescent); evergreen; resinous. Perennial (long-lived); plants with a basal concentration of leaves (when acaulescent), or with terminal rosettes of leaves; rhizomatous, or tuberous. Pachycaul. Xerophytic. Leaves small to very large; alternate; spiral; leathery; sessile; sheathing (initially), or non-sheathing (subsequently). Leaf sheaths not tubular; with free margins. Leaves simple. Leaf blades entire; solid; solid/angular (triangular or quadrangular); linear (narrowly); parallel-veined; without cross-venules; broad, thickened, distinct, closely imbricate. Leaf blade margins entire (with microscopic trichomes). Vegetative anatomy. Plants without silica bodies. Leaf anatomy. Hairs present (rarely), or absent. Extra-floral nectaries absent. Stem anatomy. Secondary thickening anomalous; from a single cambial ring.

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

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in spikes (based on contracted cymes). Inflorescences scapiflorous; terminal; complex, dense, spikelike, multiflorous, pedunculate. Flowers sessile; bracteate; bracteolate; small; regular; 3 merous; cyclic; pentacyclic. Perigone tube absent. Hypogynous disk absent. Perianth of ‘tepals’; 6; 2 -whorled; isomerous; free; petaloid (inner 3 members), or sepaloid (outer 3 dry, scarious); different in the two whorls (the outer members stiffer and shorter); white, or cream, or hyaline. Androecial members definite in number. Androecium 6. Androecial members free of the perianth; all equal; free of one another; 2 -whorled. Androecium exclusively of fertile stamens. Stamens 6; all more or less similar in shape; diplostemonous; on the receptacle. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse. Pollen shed as single grains. Gynoecium 3 carpelled. The pistil 3 celled. Carpels isomerous with the perianth. Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 3 locular; sessile. Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stigmas 1; trilobate, capitate or punctiform. Placentation axile. Ovules 3–8 per locule (‘several’); horizontal, or ascending; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit 3 celled; 3–6 seeded. Seeds endospermic. Endosperm oily. Cotyledons 1. Embryo straight, or curved (situated transversely). Testa encrusted with phytomelan.

Geography, cytology, number of species. Australian. 66 species.

Additional characters Pollen grains extended- sulcate.