Myriophyllum robustum Hook.f.
M. variaefolium var. ß Hook. f. Fl. N.Z. 1, 1852, 64.
Type locality: "Northern Island, Colenso". Type: K, "No. 112, New Zealand, Colenso". Endemic.
Aquatic or semi-aquatic herb, rooted from lower nodes; erect stems robust, to 40 cm. tall and 5 mm. in diam., sparsely branched. Lvs verticillate in whorls of c. 5, c. 3 cm. × 6-8 mm., often crowded, all pinnate to pinnatifid, segs longer and finer in lowest lvs. Fls solitary in the axils of upper lvs, sessile, hermaphrodite and protandrous; bracteoles very short, pinnati- or palmati-sect; sepals small, triangular, minutely serrate; petals pale, c. 2.5 mm. long, falling early; stamens 8, anthers 2 mm. long; ovary c. 1 mm. long, styles 4, divergent, stigmas plumose; fr. pale when ripe, often broader than long, c. 2 × 3 mm., mericarps often developing unevenly; surface smooth and rounded or occ. with a few sharp tubercles towards base.
DIST.: N., S. especially west coast. In lagoons and swamps.