340 94. POTAMOGETONACEE. 
Order XCIV. POTAMOGETONACE. 
Fl. perfect or imperfect. Perianth inferior, 4-parted, or 0, or 
replaced by a membranous spath. Stam. free, 1,2 or 4. Ovaries 
4, distinct, each with 1 ovule, and 1 sessile stigma. Fr. a drupe 
inclosing a hard nut, or a dry nut, not bursting, l-seeded. Albu- 
men 0. Embryo with a thin skin having a lateral cleft. 
1. Poramoceton. FI. perfect. Perianth 4-parted. Anth. 
4, sessile, opposite to the divisions of the perianth. Ovaries 
+, styles 0. Drupes 4, sessile.—Fl. sessile, spiked. 
Rupria. Fl. perfect. PerianthO. Stam. 2, the cells con- 
siderably separated, filaments very short scalelike. Ovaries 4, 
styles 0. Nuts 4, with long stalks.—FI. about 2 together. 
3. ZANNICHELLIA. Fl. imperfect, axillary. Barren with | 
stam. and no perianth. Fertile with a bellshaped perianth, 
persistent style, peltate stigma. Nuts 3—5 or more, very 
shortly stalked. 
to 
1. Potamoceton Linn. Pondweed. 
* JL. alternate, upper 1. floating and sometimes opposite ; stipules 
Sree. 
1. P.natans (L.); 1. all stalked, upper coriaceous floating ovate 
or elliptical plicate at the base, petioles plane-concave above, lower 
leafless petioles linear or setaceous, fr. (large) rounded on the 
back when fresh keeled when dry, peduncles equal. E. B. 1822. 
R. vii. 50.—A creeping rhizome. Lowermost |. (phyllodes) often 
quite setaceous ; upper |. more or less cordate at the base, when 
pressed flat a ridge is formed on each side of the base, jointed to 
their stalks a little below the limb. Sep. stalked, rhomboidal, 
rounded. Fr. 14—2 lin. long.—Ponds, ditches, and slow streams. 
P. VI. VIL. 
2. P. oblongus (Viv.); 1. all stalked, upper subcoriaceous 
floating oblong-elliptical subcuspidate not plicate, petioles plane- 
concave above none leafless, lower 1. linear-lanceolate, fr. minute 
obtuse and rounded on the back, peduncles equal.—E. B. S. 2849. . 
—St. ereepmg below. Petioles longer than leaves. Lower l. 
often very narrow. Spikes rather short and wregular. Sep. 
transversely elliptical, stalked. Fr. reddish, 1 lin. long, having a 
faint keel and rather obscpre lateral ridges when dry.—Ditches, 
small streams, ponds. P. VII. 
3. P. plantagineus (Duer.); 1. all shortly stalked membranous 
ond pellucid blunt not cuspidate nor plicate, upper elliptical, pe- 
tioles plane-concave above, lower l. oblong,,fr. minute rounded on 
the back when fresh keeled when dry, peduncles equal.—E. B. S.. 
