Potamogeton. | NAIADACEZ. 751 
Nortu Istranp: Auckland—Waikato River and Lake Whangape, Kirk ! 
T. F. C.; Lakes Tarawera and Rotomahana, Kirk! Hawke's Bay—Tangoia 
Lagoon, Colenso, A. Hamilton! Sourn Isntanp: Canterbury—Lake Forsyth, 
Kirk! Otago—Lake Waihola, and still waters of the Taieri Plain, Petrie! 
December—March. 
A very widely distributed plant, found in fresh or brackish waters in most. 
parts of the world. 
3. RUPPIA, Linn. 
Slender submerged much-branched herbs, usually growing in 
brackish water. Leaves alternate or opposite, filiform, with broad 
sheathing bases. Flowers minute, hermaphrodite, 2 or more on 
a spike, at first enclosed in the membranous leaf-sheath, but after 
flowering the filiform peduncle elongates greatly, and is either 
straight or spirally coiled. Perianth wanting. Stamens 2, oppo- 
site; filaments very short; anthers 2-celled, the cells distinct, 
opening outwards. Carpels 4; stigma sessile, peltate; ovule 
solitary, pendulous from the apex of the cell. Fruiting carpels 
stipitate, obliquely ovoid, obtuse or beaked. Seed uncinate ; testa 
membranous ; embryo with a large thick radicle and small incurved 
cotyledon. 
A genus of either one variable species or of several closely allied ones, 
common in brackish waters in almost all temperate or subtropical countries. 
1. R. maritima, Linn. Sp. Plant. 127.—Stems slender, filiform, 
variable in length, 6-24 in., leafy throughout. Leaves 2-5in. long, 
filiform, with broad membranous sheathing bases. Flowers 2-6. 
together, at first completely enclosed in the inflated leaf-sheath ; 
but the spike gradually emerges, and is borne up to the surface 
of the water by the usually conspicuously spirally coiled peduncle. 
Ripe carpels ;4,-41n. long, greenish, obliquely ovoid, beaked ; each 
one on a slender stipes sometimes more than lin. long.—Hook. f. 
Fl. Nov. Zel. i. 236; Handb. N.Z. Fl. 279; Benth. Fl. Aus- 
tral. vil. 174. 
NortH snp SourH Isptanps: Abundant throughout in _ brackish-water 
ponds and lagoons, not so common in fresh-water lakes and streams. De- 
cember-April. 
All the specimens I have seen have spirally coiled peduncles and rather 
broad sheaths ; but in all probability the variety (or species) rostellata will also: 
be found, which has straight or flexuous peduncles and narrow leaf-sheaths. 
4, ZANNICHELLIA, Linn. 
Slender submerged water-plants; stems filiform, branched. 
Leaves usually opposite, filiform, sheathing at the base; sheaths 
stipular. Flowers minute, axillary, moncecious, a single male and 
female enclosed in the membranous leaf-sheaths. Male flower: 
Perianth wanting. Stamen 1; filament short at first, elongat- 
ing as the flower expands; anther 2-3-celled, linear, basifixed, 
