NAIAS ?- NAIADACE At 671 
2 Zostera Stems slender, from creeping rootstocks: perianth wanting: 
ovaries and stamens alternate in 2 vertical rows on the inner side of a 
margined leaf-like enclosed spadix: ovaries pendulous: stigmas 2. 
8 Phyllospadix Stems floating, from creeping rootstocks : flowers diceci- 
ous, without perianth: anthers sessile, in 2 rows on a spadix: ovaries 
in 2 rows on the inner side of a margined enclosed spadix, ascending: 
stigmas 2, linear, sessile. 
4 Lilea Annual stemless plants: flowers moncecious; staminate in close 
' spikes on scapes under a single bract; pistillate flowers at the base of 
the leaves with very long styles, or in dense heads on scapes; stigmas 
capitate 
+ + Ovaries about 4, nearly sessile, becoming more or less stipitate. 
5 Zannichellia Leaves opposite: flowers moncecious, axillary or nearly 
so: anther solitary, on aslender naked filament: pistillate fowers 
solitary, with a cup-shaped membranaceous spatheor perianth: stigma 
peltate. 
6 Rup via Leaves alternate: flowers perfect, 2 or more on an enclosed 
spadix, at length long-exserted, without perianth: anthers 2, sessile: 
stigma depressed. 
_ * * Flowers perfect, with herbaceous 4-parted perianth, in a 
peduncled spike. 
¢ Potamogeton Ovaries and anthers 4, sessile: stigma sessile. 
. 1 NAIAS L. Sp. 1015. 
‘Slender branching aquatic wholly submerged plants with oppo- 
site, alternate or verticellate leaves with sheathing bases, and in- 
conspicuous moneecious or dicecious flowers in axillary clusters or 
solitary. Staminate flowers of a single stamen and a membranous 
tubular 4-lobed perianth within a small cup-shaped membranous 
spathe. Anther 4-celled. nearly sessile: pollen granular Pistil- 
late flowers without perianth or spathe, the oblong ovary termin- 
ated by a short style and 3-4 narrowly subulate stigmas. Fruit 
a membranous utricle, filled by the single erect anatropous seed. 
N flexilis Rost. & Schmidt Fl. Sed. 384. Stem slender, dichotomous- 
ly much branched 6-18 inches long: leaves linear, acuminate or abruptly 
acute, 6-12 lines long. 44-1 line wide, numerous and crowded upon the up- 
per part of the branches, with 25-30 minute teeth on each side; sheaths 
obliquely rounded, with 5-10 teeth on each margin: fruit e!lipsoid, with 
very thin pericarp, 1-2 lines long: style long, persistent; stigmas short: 
seed smooth, shining, straw-color, sculptured with 30-40 rows of nearly 
square or hexagonal reticulations. In ponds and streams, throughout 
nearly all parts of North America: also in Europe. 
N. Gaudalupensis Morong Mem. Torr. Bot. Club, iii, 60. Stem near- 
ly capillary 1-2 feet long, widely branched from the base: leaves numerous, 
6-9 lines long, 144-14 line wide, acute, opposite or in fascicles of 2-5, fre- 
quently recurved, with 40-50 teeth on each margin: fruit about a line long; 
pericarp dark and strongly marked by 15-20 rows of hexagonal or rectangu- 
lar reticulations which are transversely oblong: seed straw-color, not 
shining. In ponds and streams, Oregon to Nebraska and Texas: also in 
tropical America. 
2 ZOSTERA L. Sp. 968. 
Marine plants with creeping rootstocks, branching compressed 
