Amaranthaceae

Abstract

Annual or perennial herbs, subshrubs or shrubs, rarely lianes or trees. Leaves simple, alternate or opposite, exstipulate, entire or almost so. Inflorescence a dense head, loose or spike-like thyrse, spike, raceme or panicle, basically cymose, bracteate; bracts hyaline, membranous, white or coloured, subtending one or more flowers. Flowers hermaphrodite or unisexual (plants dioecious, polygamous or monoecious), mostly actinomorphic, usually bibracteolate, often in ultimate 3-flowered cymules; lateral flowers of such cymules sometimes sterile, being modified into scales, straight or hooked spines, bristles or hairs. Perianth uniseriate, membranous to firm and finally indurate, usually falling with the ripe fruit included, with or without the bracteoles. Tepals (0-1)-3-5, free or somewhat fused below, glabrous to ± pilose or lanate, green to white or variously coloured. Stamens as many as and opposite the tepals, rarely fewer or more; filaments free or commonly fused into a cup at the base, sometimes almost completely fused and 5-toothed at the apex with entire or deeply lobed teeth, some occasionally anantherous, sometimes alternating with variously shaped pseudostaminodes²; anthers 1-2-locular (i.e., dehiscing by one or two slits — unilocular anthers are bilocellate and bilocular anthers 4-locellate before dehiscence). Ovary superior, unilocular; ovules usually solitary, sometimes two to numerous, erect to pendulous, placentation basal; style very short or obsolete to long and slender; stigmas capitate (simple or penicillate) or up to 2–3 (−6) and long and slender. Fruit an irregularly rupturing capsule with thin membranous walls (sometimes called a “utricle” but this is scarcely accurate), less frequently circumscissile, rarely a berry or crustaceous. Seed globular to lenticular or ovoid, rarely arillate; embryo curved or circular, surrounding the ± copious starchy perisperm, true endosperm scanty.

The author wishes to thank Dr. G. Benl for advice on Ptilotus, Mr. T. Reynolds for advice on sources for phytochemistry in the family, Miss Susan Zmarzty, who did most of the palynological work, and Mrs. M. Harley, who also helped in this direction.