90. POTAMOGETONE.E. 
;m 1 
Older XC. POTAMOGETONE^T:. 
FI. ]U'rfeet or unisexual. Periantli inferior, 4-j)arted, or 0. 
Stain, definite, hy])oijynous. Ovaries 4, or 1, distinct, eaeliwit'i 
1 ovule. Fr. a (Irupe or nut, not bursting, 1 -seeded. Seed pen- 
dulous. Albumen 0. Embryo straight or curved, with a lateral 
cleft. 
1. PoTAMOGETON. FI. perfect. Perianth 4-])arted. Anth. 
4, sessile, opposite to the divisions of the perianth. Ovaries 
4, styles 0. l)ru)>es 4, sessile. 
2. Ruimma. F’l. perfect. Perianth 0. Stam. 2, the cells con- 
siderably scjiarated, filaments very short scalelike. Ovaries 4, 
styles 0. Nuts 4, with long stalks. 
3. Zannichellia. FI. imperfect. Male fl. with 1 stam. 
and no perianth. Fern. fl. with a bellshaped perianth, per- 
sistent style, peltate stigma. Nuts 3 — 5 or more, very 
shortly stalked. 
4. Zostera. Stam. and pistils inserted in 2 rows upon one 
side of a spadix. Sjiath linear, terminating in a leafy point. 
Fd. naked. Anth. 1. Ovary 1, style 1, stigmas 2. 
1. PoTAMOGETON Linn. Pondweed. 
* L. alternate, upper 1. floating and sometimes opposite, sti- 
pules free. 
1. P. natans (L.) ; 1. all stalked, upper coriaceous floating ovate 
or elli])tical, lower 1. linear or lanceolate or setaceous, petioles 
plano-concave above, fr. {large) rounded on the back when fresh 
keeled when dry, peduncles equal. — E. B. 1822. R. vii. t. 50. — 
A creeping rhizoma at the bottom of the water. Lowermost 1. 
often quite setaceous ; upper 1. move or less cordate at the base, 
when pressed flat a ridge is formed on each side of the base. F'r. 
2 lines long. — Ponds, ditches, and slow streams. P. VI. VII. 
2. P. oblongus (Viv.); 1. all stalked, upper coriaceous floating 
oblong-elliptical, lower 1. linear-lanceolate, petioles plano-con- 
cave above,//-, minute obtuse and rounded on the back, peduncles 
equal. — E. B. S. 2849. — St. creeping below. Lower 1. often very- 
narrow. Fr. not exceeding 1 line in length, rounded on the back 
when fresh and having 3 faint ridges when di-y. — Ditches, small 
streams, ponds. P. VII. 
3. P. plantagineus (Ducr.); 1. all stalked membranous and pel- 
lucid blunt entire, upper elliptical, lower 1. oblong, petioles plano- 
concave above, fr. minute rounded on the back when fresh acutely 
keeled when dry, peduncles equal. — E. B. S. 2848. R. vii. t. 45. 
— St. creeping below, branched, sometimes throwing out long 
