Description from Flora of China
Herbs annual or perennial, armed with stinging hairs. Stems sympodial, upper stem often zigzig, often 5-angled. Leaves alternate, petiolate; stipules caducous, intrapetiolar, connate, often broad, foliaceous; leaf blade 3-veined, margin dentate or lobed; cystoliths punctiform. Inflorescences in axillary pairs or solitary, cymes, panicles or spikes, unisexual (plants monoecious or dioecious); male inflorescence often long, flowers clustered on rachis of spikes, dichotomous cymes, or panicles; female glomerules lax or dense on rachis of scorpioid cymes, spikes, or panicles. Male flowers: perianth lobes 4 or 5, valvate; filaments inflexed in bud; rudimentary ovary conspicuous. Female flowers: perianth lobes 4, 2 or 3 lobes connate into a tube, 2 or 3-toothed, split to base on 1 side, sometimes also with a small bristle-like segment; staminodes absent. Ovary straight, ovoid; stigma subulate, papillose on 1 side; ovule orthotropous. Achene often large, slightly oblique, often compressed, verrucose; persistent stigma usually reflexed; pedicels simple or swollen. Seeds with thin or no endosperm; cotyledons broad.
The stem fibers are used to make ropes, nets, and coarse cloth and the plants are used as febrifugal medicines. The stinging hairs are very strongly irritating.
About two species: N Africa, Asia, Madagascar; one species in China.
(Authors: Chen Jiarui (陈家瑞 Chen Chia-jui); Ib Friis, C. Melanie Wilmot-Dear)