Family 1. ZANNICHELLIACEAE 
By Norman Tayvror 
Perennial marine or fresh-water plants with floating or submerged leaves, 
or both. Leaf-blades petioled or sessile, capillary or expanded into a proper 
blade, or rarely reduced to terete phyllodia. Flowers perfect or monoecious, 
in sessile or pedunculed spikes, or in clusters in the axils of the leaves. 
Perianth none, but flowers sometimes enclosed in a hyaline sheath. Androe- 
cium of 1-4 stamens. Anthers extrorse, 1-2-celled, the connective sometimes 
becoming petal-like. Gynoecium of 1-4 distinct, 1-seeded carpels. Fruits 
mostly nut-like or drupe-like, sessile or stipitate. Endosperm wanting. 
Flowers monoecious; stamen 1. 1. ZANNICHELLIA. 
Flowers perfect ; stamens more than 1. 
Stamens 2; connective of the anther not dilated ; fruit stipitate. 2. RUPPIA. 
Stamens 4; connective of the anther dilated and perianth-like ; fruit sessile. 3. POTAMOGETON. 
1. ZANNICHELLIA IL. Sp. Pl. 969. 1753. 
Stem simple or branched, submerged. Leaves all linear, submerged, entire. Stipules 
sheathing the leaf-bases, or free. Flowers axillary, monoecious, enclosed in a hyaline, 
deciduous spathe. Perianth none. Staminate flower of a single anther, on a short fila- 
ment; anther 2-celled. Pistillate flowers 2-5; carpels flask-shaped, tapering into the short 
style; stigma cup-shaped, with dentate or angled edges. Mature fruit a stipitate, smooth 
or muricate nutlet. Embryo coiled at the cotyledonary end. 
Type species, Zannichellia palustris YL. 
1. Zannichellia palustris L. Sp. Pl. 969. 1753. 
Zannichellia intermedia Torr.; Beck, Bot. 385. 1833. 
Stems slender, simple or branched; leaves all submerged, linear, capillary, 2-10 cm. 
long, acute or almost pungent at the apex, l-nerved; stipules scarious, free from the leaf- 
bases, scarcely 2cm. long; staminate and pistillate flowers in the same leaf-axil, subtended 
or enclosed by a hyaline bract; staminate flower of a single 2-celled anther on a slender 
filament; pistillate flowers of 2-10 carpels, sessile at first, often pedicellate after anthesis ; 
carpels flask-shaped, ribbed or toothed on the margins, or sometimes smooth; style re- 
curved, persistent; stigma cup-shaped, with dentate or angled edges; mature fruit 2-4 
mm. long, rarely pitted. 
TYPE LOCALITY : Europe. . : 
DISTRIBUTION : In fresh or brackish water nearly throughout North America, except the 
extreme north. 
ILLUSTRATIONS: Ann. Sci. Nat. 11.9: 1.3, f. 6; E. & P. Nat. Pil. 21: f 161 a-c ; Mem. Torrey 
Club 3?: pl. 64; Britt, & Brown, Ill. Fl. f. 178. 
2. RUPPIA L. Sp. Pl. 127. 1753. 
Perennial marine or fresh-water herbs. Stems simple or branched, submerged. Leaves 
linear, entire, 1-nerved, acute at the apex, broader and sheathed at the base; stipular 
sheaths clasping the leaf-bases. Flowers perfect, terminating a spadix-like peduncle. Per- 
ianth none, but the flowers often enclosed in the sheathing leaf-bases when young. Stamens 
2; anthers 2-celled, sessile. Carpels 4, sessile at first, at length stipitate ; stigmas sessile, 
or at the end of a long or short style, peltate. Mature fruit on the end of a long pedicel 
which recoils after the fruit drops off. Drupelet oblique or equilateral, stipitate, crowned 
with the long or short style. Embryo curved, ovoid. 
Type species, Ruppia maritima L. 
Stipular sheaths 10 mm. long or less, the free part shorter. 1. R, maritima, 
Stipular sheaths 15 mm, long or more, the free part as long. 2. R. occidentalis. 
VotuMmeE 17, Part 1, 1909] 18 
