South Island: Canterbury-Broken River, J. D. Enys and T.F.C.; Rangitata Valley, Haast! Lake Tekapo and Tasman Valley, T.F.C. Otago—Ophir, Black's, Petrie! 2000–3000 ft. December–January.
A plant with a wide distribution in the Northern Hemisphere, also found in extratropical South America, but not yet detected in Australia.
2. POTAMOGETON, Linn.
Perennial aquatic herbs. Stems slender, simple or branched. Leaves wholly submerged and translucent, or floating and opaque, alternate or opposite, entire or toothed; stipules intrafoliar, free, or adnate to the petiole or base of the leaf. Flowers small, green, hermaphrodite, ebracteate, sessile in a dense spike on an axillary peduncle arising from a membranous spathe. Perianth-segments 4, small, herbaceous, concave, valvate. Stamens 4, inserted at the base of the segments; anthers sessile, 2-celled, extrorse. Carpels 4, sessile, distinct, 1-celled; stigma oblique, decurrent; ovules solitary, aflixed to the inner angle of the cell, campylotropous. Ripe carpels or drupelets 4, small, coriaceous or spongy, ovoid or subglobose, obtuse or beaked by the recurved persistent stigma, 1-seeded. Seed curved, reniform; testa membranous; embryo with a large radicle and narrow incurved cotyledon.
A genus widely spread in the fresh or brackish waters of almost all temperate or subtropical regions, more rare in the tropics. Species variously estimated at from 40 to 100 or more, according to the different views of authors, extremely variable, and most difficult of discrimination. The New Zealand forms have never been carefully sought for, and in all probability other species will be added to those described herein.
| A. Floating leaves more or less coriaceous, with a broad long-petioled lamina, different in shape from the membranous submerged ones. Stipules free. | |
| Floating leaves 2–4 in., biplicate at the base. Submerged leaves wanting or reduced to phyllodes. Fruit large, ⅙ in. long, keeled on the back when dry | 1. P. natans. |
| Floating leaves 1–3 in., not plicate at the base. Submerged leaves few, linear-lanceolate. Fruit small, 112–110 in., rounded on the back | 2. P. polygonifolius. |
| Floating leaves ¾–1¾ in. Submerged leaves numerous, 2–4 in. Fruit small, 110 in., keeled on the back when dry | 3. P. Cheesemanii. |
| B. Leaves all submerged and uniform, sessile, membranous. | |
| Leaves 1–4 in. by ⅛–¼ in., linear-ligulate, obtuse; stipules free, lacerate. Spike dense | 4. P. ochreatus. |
| Leaves 2–4 in. by 120–115 in., very narrow-linear or filiform; stipules adnate. Spike interrupted | 5. P. pectinatus. |
1. P. natans, Linn. Sp. Plant. 126.—Stems creeping below, long or short, simple or sparingly branched, terete. Floating leaves on long petioles; lamina 2–4 in. long, oblong or elliptic or elliptic-lanceolate, acute or subacute, subcordate and shortly biplicate at the base, coriaceous, 20–30-nerved with copious cross-veins and
