Annual or perennial herbs or subshrubs, rarely scandent. 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 to white or coloured, subtending one or more flowers. Flowers hermaphrodite or unisexual (plants dioecious or monoecious), actinomorphic, commonly bibracteolate, frequently in ultimate 3-flowered cymules; lateral flowers of such cymules sometimes modified into scales, spines or hooks. Perianth uniseriate, membranous to firm and finally ± indurate, usually falling with the ripe fruit included, tepals free or somewhat fused below, frequently ± pilose or lanate, green to white or variously coloured. Stamens as many as and opposite to the petals, rarely fewer; filaments free or commonly fused into a cup at the base, alternating with variously shaped pseudo-staminodes or not, sometimes almost completely fused and 5-toothed at the apex with entire or deeply lobed teeth, some occasionally anantherous. Ovary superior, unilocular; ovules 1-many, erect to pendulous, placentation basal; style very short to long and slender; stigmas capitate to long and filiform. Fruit an irregularly rupturing or circumscissile capsule (utricle) usually with thin, membranous walls, rarely crustaceous or a berry. Seeds round to lenticular or ovoid, embryo curved or circular, surrounding the ± copious endosperm.
A large and almost exclusively tropical family of some 65 genera and over 1000 species, including many cosmopolitan “weeds” and a large number of xerophytic plants.
Type genus: Amaranthus L.
In some tropical Floras keys to the Amaranthaceae have been supplied using as primary division the character of opposite or alternate leaves. Of Pakistani genera of this family Deeringia, Celosia, Bosea, Amaranthus and Digera appear to have leaves constantly alternate, and Pupalia, Achyranthes, Alternanthera, Gomphrena and Iresine opposite. Unfortunately, both Aerva sanguinolenta and Nothosaerva brachiata vary with either opposite or alternate leaves and branches.
Acknowledgement: We are grateful to the United States Department of Agriculture for financing this research under P.L. 480.