Amaranthus subg. Albersia
Plants monoecious (in some species staminate flowers are rare). Stems ascending, prostrate, or erect, not fleshy (fleshy in A. pumilus and A. californicus). Inflorescences mostly or exclusively axillary, glomerules or short spikes, if terminal inflorescences also developed, then axillary clusters present to base of plant. Pistillate flowers: tepals usually (1–)3–5. Utricles indehiscent, tardily dehiscent, or dehiscence circumscissile.
North America, South America, Eurasia, Africa.
Species 25+ (17 in the flora).
Subgenus Albersia remains the most diverse infrageneric group of Amaranthus. Sections have been proposed in the subgenus (see S. L. Mosyakin and K. R. Robertson 1996). In particular, species with circumscissile fruits are placed in sect. Pyxidium Moquin-Tandon; plants with indehiscent fruits and usually three elliptic to linear tepals are members of sect. Blitopsis Dumortier; and plants with indehiscent utricles and five or, rarely, four spatulate or at least distinctly obovate tepals are housed in sect. Pentamorion (G. Beck) Mosyakin & K. R. Robertson (= Euxolus Rafinesque sect. Pentamorion G. Beck). Many species of subg. Albersia evidently belong to yet undescribed infrageneric entities and thus currently remain unassigned to any particular sections. Because of that we refrain from using here the sections of Amaranthus subg. Albersia.