748 NAIADACEZ. [ Triglochin. 
SoutH Isntanp: Canterbury— Broken River, J. D. Hnys and 7. F. C.; 
Rangitata Valley, Haast! Lake Tekapo and Tasman Valley, 7. #. 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, 1l-celled; stigma oblique, decurrent; ovules 
solitary, affixed 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 tem- 
perate or subtropical regions, more rare in the tropics. Species variously esti- 
mated 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 swomerged ones. Stipules free. 
Floating leaves 2-4 in., biplicate at the base. Submerged 
leaves wanting or reduced to phyllodes. Fruit large, 
din. long, keeled on the back when dry 1. P. natans. 
Floating leaves 1-3in., not plicate at the base. Sub- 
merged leaves few, linear-lanceolate. Fruit small, 
zy5-z4 in., rounded on the back oe . 2. P.polygonifolius. 
Floating leaves ?-ljin. Submerged leaves numerous, 
2-4in. Fruit small, qo in., keeled on the back when 
dry 3. P. Cheesemani. 
B. Leaves all submerged and uniform, sessile, membranous. 
Leaves 1-4 in. by 4-+in., pacer Lgulate, obtuse ; stipules 
free, lacerate. Bae dense .. 4. P. ochreatus. 
Leaves 2—4 in, by sy-7s in., very narrow- ‘linear or - filiform ; 
stipules adnate. Spike interrupted ie .. 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 
