ZANNICHELLIACEAE 39 



1. SPARGANIUM L. 



Characters of the family. BUR-REED. Spring and summer. 



Nutlets stipitate, fusiform: stigmas mostly solitary. 



Upper leaves with neither sac-like bases nor hyaline margins: achenes abruptly narrowed into 

 the slender style. 1. S. androcladum. 



Upper leaves with sac-like bases and hyaline margins: achenes gradually 



narrowed into the conspicuous styles. 2. S. Americanum. 



Nutlets sessile, obovoid or obpyramidal: stigmas mostly 2. 3. S. eurycarpum. 



1. Sparganium andrdcladum (Engelm.) Morong. Plant 3-10 dm. tall: 

 inflorescence branched: staminate heads mostly less than 1 cm. thick: pistillate heads 

 becoming 1-2 cm. thick: nutlets abruptly narrowed at the apex, the stigma linear, 

 about 2 mm. long. 



In shallow water, Newfoundland to Minnesota, Florida and Alabama. 



2. Sparganium Americanum Nutt. Similar to S. androcladum, but inflores- 

 cence simple: nutlets gradually narrowed at the apex, the stigma oblong, 1 mm. long. 



On muddy shores and in ponds, Nova Scotia to Iowa, South Carolina and Oklahoma. 



3. Sparganium eurycarpum Engelm. Plants 8-20 dm. tall, inflorescence 

 branched: staminate heads about 1 cm. thick: pistillate heads becoming 2-2.5 cm. 

 thick: nutlets rounded or depressed at the apex, the stigmas filiform, 2 mm. long. 



In marshes or along streams, Newfoundland to British Columbia, Florida and California. 



Order 2. NAIADALES. 



Perennial aquatic or marsh herbs. Leaves various, sometimes mere phyl- 

 lodia. Flowers usually symmetrical. Perianth wanting or imperfect. Androe- 

 cium usually of 1-4 stamens. Gynoecium simple or several-carpellary. 



Gynoecium of distinct carpels. Fam. 1. ZANNICHELLIACEAE. 



Gynoecium of one carpel, or of united carpels. 



Staminate and pistillate flowers borne alternately on a one- 

 sided spadix, laterally attached. Fam. 2. ZOSTERACEAE. 

 Staminate and pistillate flowers borne in the leaf-axils. 



Staminate flowers consisting of 2 anthers terminating an 



elongated pedicel: perianth wanting: stigmas filiform: 

 acaulescent plants with entire leaf-blade 



les. Fam. 3. CYMODOCEACEAE. 



Staminate flowers sessile or nearly so, cpnsisting of an 

 anther surrounded by the perianth: stigmas subulate; 

 caulescent plants with spiny toothed leaf blades. Fam. 4. NAIADACEAE. 



FAMILY 1. ZANNICHELLIACEAE Dumort. TONDWEED FAMILY. 



Aquatic caulescent herbs. Leaves alternate, filiform or with broad entire 

 blades. Flowers perfect or monoecious in spikes or clusters from a spathe. 

 Androecium of 1 or mostly of 2-4 distinct stamens. Gynoecium of several dis- 

 tinct carpels. Fruit a cluster or spike of drupelets. 



Stamens 2 or sometimes solitary , the connectives without appendages: drupelets manifestly stipitate. 



Stigma terminating a long style: anther 1. 1. ZANNICHELLIA. 



Stigma sessile: anthers 2. 2. RUPPIA. 



Stamens 4, the connectives with dilated appendages: drupelets sessile. 3. POTAMOGETON. 



1. ZANNICHELLIA L. 



Delicate herbs of fresh or brackish water. Leaves with narrow blades and 

 inconspicuous bases. Flowers monoecious; staminate with 1 stamen and pistillate 

 with 2-6 carpels, together. Drupelets clustered, curved, crested. 



1. Zannichellia palustris L. Stems 2-7 dm. long: leaves 2-7 cm. long, acute: 

 drupelets 2-4, or sometimes 6, together, the body 2-4 mm. long, short-stipitate. 



In ponds and ditches, nearly throughout North America. Also in the Old World. 

 Spring and summer. 



2. RUPPIA L. 



Delicate herbs of salt or brackish water. Leaves with slender blades and con- 

 spicuous bases. Flowers perfect. Stamens 2. Carpels 4. Drupelets clustered, 

 oblique, crestless. DITCH-GRASS. 



1. Ruppia maritima L. Stem 3-10 dm. long: leaves 2.5-10 cm. long, capillary 

 at the apex: drupelets few, the body ovoid, gibbous at the base, long-stipitate. 

 Coasts and interior of North America. Also in the Old World. Summer. 



