10 ZANNICHELLIACEAE. 



angles of the fruit or with 2-3 outer ones, spatulate or eroded, equal- 

 ing the fruit. 



Occasional along streams, usually growing with Typha. Los 

 Angeles River; Ballona Creek; New River near Alamitos, May- 

 June. 



2. S. multipedunculata (Morong) Rydb. A slender plant, with 

 slender fusiform nutlets, widest near the middle. 

 Bluff Lake, San Bernardino Mountains, Hall. 



Family 4. ZANNICHELLIACEAE. 



PoNDWEED Family. 



Aquatic plants entirely submerged or with floating 

 leaves. Stems jointed, usually branched. Leaves capil- 

 lary to lanceolate or with broad floating blades, sheath- 

 ing at the base. Flowers small, without perianth, 

 commonly borne In spikes or axillary clusters. Stamens 

 1-4, with extrorse anthers. Ovaries 1 to 4, mostly 

 distinct, 1-celled, 1-ovuled. Carpels rarely dehiscent; 

 endosperm none; embryo often curved. 



Flowers perfect; stamens more than L 



Fruit sessile; stamens 4. L Potamogeton. 



Fruit stalked; stamens 2. 2. Ruppia. 



Flowers monoecious; stamens L 3. Zannichellia. 



L POTAMOGETON L. Pond weed. 



Perennial herbs. Leaves alternate or the uppermost 

 often opposite, often of 2 kinds, submerged and float- 

 ing, the floating elliptic or ovate, the submerged linear. 

 Spikes sheathed by the stipules In the bud. Peduncles 

 axillary, bearing small perfect flowers. Perianth seg- 

 ments 4, herbaceous, concave, valvate In the bud, short- 

 clawed. Stamens 4, Inserted on the claws of the peri- 

 anth segments; anthers sessile. Ovaries 4, sessile, dis- 

 tinct, 1-celled, 1-ovuled, attenuate into a short erect or 

 recurved style. 



With floating and submerged leaves. 

 Floating leaves thick; fruit pitted on 



the sides, 2-grooved on the back. L P. natans. 

 Floating leaves thin; fruit smooth on 



the sides, 3-keeled dorsally. 2. P. americanus . 



With submerged leaves only. 



Leaves 2 mm. wide, 3-nerved. 3. P. foliosus californicus. 



Leaves capillary, 1-nerved. 4. P. pectinatus. 



