1Small, caespitose herb, glabrous in all parts. Stems rooting at the nodes, at least at the base, apex often ascending. Sepals with a thickened and shallowly cordate base. Anthers 0.3-0.7 mm long.
1'Plant hairy, at least in the younger parts. Stems not rooting at the nodes, generally erect. Base of the sepals not thickened and subcordate. Anthers 0.8-2.3 mm long.
2Fruit with 8 longitudinal ridges alternating with 8 rows of (3-4) blunt-spiny tubercles, glabrous or appressedly hairy only at the apex.
2'Fruit without rows of intercostal tubercles, or occasionally with 1 (-3) blunt, low tubercles between the ribs, and then the fruit covered with appressed, curved hairs.
3Robust plants with semi-woody, stiff stems, mostly very much branched. Leaves decussate or, especially in the middle of a branch, in whorls of 3-4; if decussate, then the index of the leaves of the main stem 1.5-2.2.
3'Perennial, slender herbs, the stem mostly branched only at the base, rather thin. Leaves always decussate; leaf-index (2-)2.8-4(-5.5).
4Anthers 8. Ripe fruit erecto-patent to patent, mostly not thickened below the sepals, 0.7-1 by 0.8-1 mm (excluding the sepals), with a granular surface, the ribs often ± tuberculate, sometimes with l(-3) intercostal tubercle(s). Inflorescence mostly much branched.
4'Anthers 4. Ripe fruit nodding, with a distinct, ± triangular thickening at the base of the sepals, 1.3-1.6 by 1-1.3 mm (excluding the sepals), the ribs smooth, the surface in between smooth or granular. Inflorescence little or not branched.