Flora of New Zealand Series

Glab. branching herb up to 2 dm. or more long; stems creeping, rooting at nodes, sts floating; stock slender to stout, erect or ascending, sts moniliformly thickened. Radical lvs in tufts at nodes, on slender to filiform petioles 2-10-(15) cm. long; sheath membr., delicate. Lamina obovate-cuneate to suborbicular to reniform in outline, 0·5-4 cm. diam.; flabellately divided to base into 3-5-(7) segs; these narrow-cuneate to linear ± deeply toothed, rarely entire. Lower cauline lvs similar, smaller; upper reduced to bracts 1 cm. or less long. Peduncles lf-opposed, 4-10 cm. long; fls 5-7-(10)mm. diam., solitary or paired; sepals 5, spreading, 3-5 mm. long; petals 5-10, yellow, 3-6 mm. long, narrow-oblong; gland 1 well above base. Fruiting heads globose, ± 7 mm. diam.; receptacle glab.; achenes ± turgid, glab., 1·5-2 mm. long, keeled, obliquely obovoid; style 1·5-2 mm. long, subulate, ± recurved at apex.

DIST.: N., S., St., Ch. Lowland to montane swamps, wet ground and still waters throughout.

FL. 10-3. FT. 10-4. Also occurs in Australia, Tasmania.

The complex of forms placed under this name are conventionally divided into the following "varieties", but the status of the different forms has not been adequately studied.

1. var. major Benth. Fl. Aust. 1, 1863, 14. R. incisus Hook. f. Fl. N.Z. 1, 1852, 10, t. 4. R. amphitricha Col. in T.N.Z.I. 17, 1885, 237. This group includes forms with very narrow ± deeply toothed segs. Hooker's R. incisus was based on small plants: " East coast, Colenso. Banks' Peninsula, Raoul. Canterbury and Otago, Lyall." R. amphitricha Col. was gathered by him "In muddy watercourses, edges of woods near Norsewood". The achenes are described as "rugosely papillate when mature".

2. var. subfluitans Benth. Fl. Aust. 1, 1863, 14. R. inundatus R. Br. ex DC. Syst. 1, 1817, 269. Here are placed forms with small less-divided lvs and with very small fls and achenes ― plant often floating.

3. var. inconspicuus Benth.loc. cit.  R. inconspicuus Hook. f. Fl. Tasm. 1, 1855, 8, t. 2B. Here are grouped very small slender plants, lf-segs 3-fid, fls very small.

4. var. glareosus Ckn. et Allan in T.N.Z.I. 56, 1926, 33. This was based on very robust plants of coastal gravel or sand found on Ninety-mile Beach, Canterbury and near mouth of Ashburton River. Rhizomes far-spreading; petals obovate-oblong.