NAIADACE^. 
391 
Order OIL NAIADACEiE. 
Flowers monochlamydeous or achlamydeous, hermaphrodite or 
monoicous. Perianth when present herbaceous and inferior. Stamens 
1-4, hypogynous ; anthers 1-2- rarely 4-celled ; pollen globose or 
tubular. Ovary of 1-4 1-celled carpels ; ovules except in Ualophila 
solitary in the cells ; style often oblique ; stigma usually peltate, 
oblique. Fruit indehiscent, dry or rather fleshy. Seed usually ex- 
albuminous. — Water plants, with various foliage and inflorescence, the 
flowers always minute. Distrib. Cosmopolitan. Species 100. 
Ovules solitary. Special spathe none. 
Flowers in spikes 1. Potamogeton. 
Flowers 1-2, sessile or stalked in the axils of the leaves. 
Flowers hermaphrodite, without any perianth ... 2. Ruppia. 
Flowers monoicous, the female with a perianth . . . 3. Zannichellia. 
Ovules numerous. Flowers in a special spathe . . . *. 4. Halophila. 
1. POTAMOGETON, Linn. 
Flowers hermaphrodite, monochlamydeous, in dense peduncled 
spikes. Perianth herbaceous, of 4 valvate free inferior segments. 
Stamens 1 ; anthers nearly sessile, 2-celled. Ovary of 4 free sessile 
carpels ; ovule solitary in each carpel, ascending ; stigma oblique, peltate, 
nearly or quite sessile. Fruit drupaceous, indehiscent, with a tough peri- 
carp. — Aquatic herbs, with leaves mostly alternate, all alike mem- 
branous and submerged, or some floating different in shape and firmer 
in texture. Distrib. Cosmopolitan. Species 50. 
Stipules free. Leaves many -nerved. 
Upper leaves floating, suhcoriaceous ....... 1. P. natans. 
All the leaves submerged and membranous. 
Leaves large, lanceolate 2. P. ltjcens. 
Leaves small, ligulate 3. P. crispus. 
Stipules adnate to the mostly 1 -nerved leaf 4. P. pectin atus. 
1. P. natans, Linn . ; Kuntli, Enum. iii, 127. Stems comparatively 
stout, reaching a length of several feet. Submerged leaves petiole-like, 
channelled, alternate. Floating leaves many, upper opposite, long- 
petioled, oblong, 2-4 in. long, 1-1| in. broad, rounded to both ends, 
suhcoriaceous, brownish-green, with 6-12 arching ribs on each side, 
connected by distinct transverse veinlets ; stipules l-l^ in. long, free, 
lanceolate. Peduncle ± in. thick, longer than the spike. Spike dense, 
1-1| in. long. Drupes £ in. long, oblique obovoid, keeled, with a 
short beak from the ventral angle. P. indicum, Roxb. FI. Ind. i. 
452. 
Mauritius and Seychelles, common in ponds and still waters. Cosmopolitan. 
2. P. lucens, Linn. ; Kuntk, Enum. iii. 132. Stems T V in. thick, 
