Alismacee. | FLORA OF TASMANIA. 41 
that separate and become pedicelled as fruit is matured. Sepals six, broad, rounded. Stamens six. Ovaries six, 
with recurved, rough stigmas.  Carpels six, obliquely linear or ovate, with spreading, curved points, straight or 
twisted, 4-4 inch long.—Endlicher separates this from the genus and Natural Order of Triglochin, on account of 
the valvate perianth, two ovules, and embryo with a large cotyledon, in all which characters, and particularly in the 
partially floating leaves, it approaches Potamogeton ; but not only is the whole habit and appearance that of Triglo- 
chin (in which Mr. Brown places it), but I find the «estivation partially imbricated (as much as in some Triglochins), 
only one ovule in all the specimens 1 have examined, and the form of the embryo varies with that of the carpels in 
the different species of the genus. 
Gen. If. POTAMOGETON, Z. 
Flores hermaphroditi. Sepala 4, valvata. Stamina 4, antheris extrorsis. Ovaria 4, sessilia, unilocu- 
laria; ovulo 1, ascendente, infra apicem loculi affixo; stigmate sessili, obliquo. Carpella 4, coriacea v. nu- 
cumentacea. Semen curvatum, exalbuminosum ; testa tenui; radicula incrassata, infera.— Herbs aquatice ; 
caulibus repentibus, demersis ; foliis alternis, rarius oppositis, polymorphis ; stipulis? intrafoliaceis ; spicis 
pedunculatis, axillaribus, basi vaginatis. 
Fresh-water herbs, with leaves often of two forms, the lower linear, grass-like, green, and submerged, the 
upper brown and floating, and short, axillary, or terminal spikes of inconspicuous green flowers that project above- 
water. In shallow places the lower leaves are often undeveloped; in deeper the upper floating ones are sometimes 
fewer in proportion. The depth of water and its rapidity, if flowing, cause great variation in their form, number, 
and size. The species are numerous, and many are found in all temperate and even tropical parts of the world. 
— Flowers few or many, sessile on short or long fleshy peduncles. Perianth of four nearly sessile concave sepals, 
valvate in wstivation. Stamens four, sessile, opposite the sepals; anthers two-celled. Ovaries four, sessile, one- 
celled, with one curved ascending ovule attached to the axis above the middle. Stigma sessile near the apex. 
Carpels four, coriaceous or bony. Seed exalbuminous; testa membranous; radicle thick, pointing downwards. 
(Name from rorapos, a river, and yerrov, a neighbour.) 
1. Potamogeton natans (Linn. Sp. Pl. 182); foliis natantibus petiolatis elliptieis oblongis oblongo- 
rotundatisve basi subcordatis rotundatis subacutisve, submersis linearibus membranaceis v. nullis, stipulis 
liberis, nucibus dorso carinatis.—Br. Prodr. 343 ; Fl. N. Zeal. i. 236. (Gunn, 148.) 
Var. B. minor ; foliis minoribus elliptico-lanceolatis. 
Has. Ponds and still rivers, abundant, Brown, etc.—(v.v.) Var. 8. Lake River, Grindelwald, 
Gunn. i 
DisrriB. Over most parts of the world, from the Arctic Circle to the Cape of Good Hope, South 
Chili, New Zealand, and Australia; also found in the Pacific Islands. 
A common and very variable plant, often covering the surface of the water with its red-brown foliage.— Leaves 
floating, 1-3 inches long, stalked, elliptical or oblong, more or less broad and sharp at both ends, or blunt or cor- 
date at the base; submerged leaves none, or linear, green, membranous. Spike 1-2 inches long. Nuts keeled at 
the back.—The var. ß resembles the European P. heterophyllus, and has smaller, sharper leaves, partly owing to 
its growing in running water, and partly to the elevation of its habitat (1500 feet). I have not seen its fruit. 
2. Potamogeton heterophyllus (Schreb. Spic. Fl. Lips. 21 ?) ; foliis natantibus petiolatis oblongis 
ellipticis elliptico-lanceolatisve, submersis membranaceis sessilibus v. breve petiolatis lanceolatis utrinque 
angustatis integerrimis crispatis denticulatisve, stipulis nervosis, pedunculis superne incrassatis.— Engl. 
Bot. t. 1285. 
Has. Derwent River, above New Norfolk, Gunn.—(v. v.) 
DrsrarB. Europe, India, and probably many other places. 
VOL. II. ; 
