Polychroa Loureiro, nom. rej.

Herbs or subshrubs, without stinging hairs. Leaves apparently alternate, distichous; nanophylls present or absent, opposite to normal leaves; stipules 2; leaf blade 3-veined, one major lateral vein sometimes inserted above the base, or pinnately veined, base asymmetric, margin entire or serrate; cystoliths mostly present, linear or fusiform. Inflorescences axillary, cymes of unisexual flowers (plants monoecious or dioecious); male ones usually pedunculate; female ones pedunculate or sessile, bracteose, rarely with discoid receptacle and involucre. Male flowers: perianth lobes 4 or 5, elliptic, connate 1/2 of length, slightly valvate, apex usually corniculate; stamens as many as and opposite to perianth lobes; filaments inflexed in bud; rudimentary pistil small. Female flowers: perianth lobes 4 or 5, distinct, longer than or as long as ovary, usually unequal, apex usually corniculate; staminodes as many as and opposite to perianth, scale-like. Ovary straight, ellipsoid; style absent; stigma penicillate; ovule orthotropous. Achenes ovoid or ellipsoid, slightly flattened, usually tuberculate.

About 60 species: tropical and subtropical Asia, Pacific islands; 20 species (nine endemic) in China.

(Authors: Lin Qi (林祁); Ib Friis, C. Melanie Wilmot-Dear)