Stems to 1 m. Leaves yellowish green, 2--4 × dichotomously divided, whorls 2.5--6 cm in diam.; segments linear to filiform, 1--1.2 cm × 0.2--2 mm, bases occasionally inflated. Flowers unknown. Achene brown or dark green, 3.5--4 × 2--2.5 mm, surfaces tuberculate to papillate, with plate-like ridges that occasionally become spiny, margins winged or wingless, entire or with 1--8 slender spines, 0.1--2.5 mm; basal spines 2, 1.5--6 mm; terminal spine (persistent style) 1--1.5 cm. Fl. and fr. Jul--Oct.
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