Potamogeton pectinatus L.
Fennel-leaved pondweed.
Type locality: European. Cosmopolitan.
Rhizome extensively creeping, forming swollen buds in autumn. Branches slender, much-branched, sts very long. Stipule adnate to lf-base, open but sheathing stem for 1–4 cm., the free ligular portion membr., c. 5 mm. long. Lvs all submersed, 5–12 cm. × c. 1 mm., entire, very narrow-linear, us. tapered to ± acute tip, membr., ∞ transverse veins us. visible. Peduncles slender, short or long. Spike discontinuous, 2–4 cm. overall, the lower whorls well separated. Achene c. 3 × 2.5 mm., light pinkish brown, rather plump and rounded, without prominent keel or beak.
DIST.: N., S.
In fresh or brackish waters.
FL. 1–2 FT. 1–3.
The above description is based essentially on N.Z. plants. This sp., with its very narrow lvs, adnate stipules, swollen rhizome buds and interrupted infl., belongs to subgenus Coleogeton (Reichb.) Raunk., and stands apart from the other N.Z. spp. which are placed in subgenus Potamogeton.
