26 ENGLISH BOTANY. 
a short style, undivided. Fruit of 4 subdrupaceous achenes, or of 
fewer by abortion. 
Herbs growing in fresh or brackish water, with submerged 
translucent leaves with cancellate, more rarely parallel venation, some- 
times with the upper leaves floating and more or less coriaceous. 
The derivation of the name of this genus of plants is from xorapdc, river, and 
yeizwy, neighbour, because it grows in or near rivers. 
Section L—PLANTAGINIFOLIA. 
Leaves all oblong or elliptical or oval, translucent, alternate, and sub- 
merged, or the upper ones opposite and sometimes floating and 
coriaceous, with involute vernation, with ribs connected by cross 
veins. Stipules free from the leaves or leaf-stalks. Peduncles axillary 
or terminal. Spikes many-flowered, more or less elongate, dense. 
Sus-Section I.—NATANTES. 
Stem simple or slightly branched towards the apex, without barren 
branches from the lower part of the flowering stems. Upper leaves 
stalked, coriaceous or subcoriaceous, rarely membranous or translucent. 
Peduncles axillary. 
. SPECIES I—POTAMOGETON NATANS. Linn. Auct. 
Pirate MCCCXCIX. 
Reich. Ic. Fl. Germ. et Helv. Vol. VII. Tab. L. Fig. 89. 
Billot, Fl. Gall. et Germ. Exsice. No. 2381. 
Stems round, simple or nearly so. Lower leaves alternate, submerged, 
linear, chanelled, opaque, with numerous longitudinal ribs; upper leaves 
floating, mostly alternate, stalked, oblong-oval or oval, subcordate or 
rounded at the base, coriaceous, the coriaceous texture extending a 
short distance down the petiole, with numerous ribs connected by trans- 
verse veins which are indistinct if the dried leaf is held against the 
light. Stipules very large, fibro-scarious, not winged on the back. 
Peduncles axillary, rather thick, not enlarged upwards. Sepals with 
their lamina roundish-rhomboidal. Fruiting-spike cylindrical, many- 
flowered, dense. Fruit* olive, large, roundish-obovate, slightly com- 
pressed, convex on the upper margin, semicircular and keeled on the 
lower, with a short beak forming a continuation of the upper margin. 
see | 
* Jn this order it is the dried fruit which is described. 
