Key for Amaranthaceae

1Leaves alternate
1'Leaves opposite
2Flowers in simple spikes, not glomerulate; tepals more than 4 mm
2'Flowers in glomerules, these in spikes that may be further branched; tepals less than 4 mm
3Herbs; flowers unisexual; top of ovary rounded or thickened, but not with upturned rim; seed exarillate
3'Lianas (climbing subshrubs); flowers unisexual or bisexual; top of ovary with upturned rim; seed arillate
4Plants prostrate, creeping or mat-forming (growing on beaches or in sandy places)
4'Plants erect or only partly decumbent
5Leaves ovate to elliptic or broadly oblanceolate, not succulent; tepals glabrous or pubescent; pseudostaminodia present
5'Leaves linear to linear-spathulate, succulent; tepals glabrous, except ciliolate at base; pseudostaminodia obscure or absent
6Inflorescence of 1-3 slender spikes, each generally several dm long, or spiciform; flowers reflexed early in development
6'Inflorescence paniculate, capitate, or if spicate, then at most a few cm long; flowers reflexed
7Flowers not in glomerules (except A. brasiliensis); bracts white, hyaline; bracteoles rigid, subulate, awned, but not hooked
7'Flowers in few-flowered, shortly pedunculate glomerules, in glomerules stiff hooked spines present; bracts and bracteoles modified into hooked spines
8Inflorescence capitate, immediately subtended by a pair of involucral leaves; filament-tube extending beyond ovary
8'Inflorescence not capitate or, if so, then the head not immediately subtended by a pair of leaves; filament-tube (and pseudostaminodia if present) forming cup shorter than ovary
9Inflorescence paniculate
9'Inflorescence capitate or short-spicate
10Panicle with a diffuse, filigree-like aspect, branches spike-like, flowers not in heads, flowers bisexual or unisexual
10'Panicle branches not diffuse, usually (e.g., except in P. grandiflora) terminating in a 4-7 mm hemispherical head; flowers bisexual
11Tepals glabrous inside; pseudostaminodia present
11'Tepals with a short or long tuft of hairs inside; pseudostaminodia absent