NAIADACEiE. 



99 



1. W. lingulata Hegelm. Fronds at maturity solitary or rarely 

 in 2's, broadly tongue-shaped, £ to 1£ lines wide, \\ to lines long, 

 cavernous throughout the lower central portion; reproductive pouch 

 triangular. 



Irrigation canals, Kern Co., Thompson. 



8. NAIADACE/E. Pondweed Family. 



Aquatic plants entirely submerged or with floating leaves. Stems 

 jointed. Leaves linear and grass-like or some with broad floating 

 blades, sheathing at base or with sheathing stipules. Flowers incon- 

 spicuous, naked or with a very small calyx, commonly borne on a 

 short spike or spadix, which bursts from an enclosing greenish bract 

 or spathe. Ovaries 1, or 2 to 4, distinct, free from the calyx if that be 

 present, 1-celled, 1-ovuled. 



Flowers perfect. 



Sepals 4, distinct . 1. Potamogkton. 



Sepals none 2. Ruppia. 



Flowers monoecious or dioecious. 

 Leaves entire. 



Pistils about 4, borne in a cup-shaped involucre; fresh water ponds or 



streams 3. Zannichellia. 



Pistils many, borne oj\ the side of a linear spadix; maritime. 

 Flowers monoecious; fruit ovoid; leaves 2 to 4 lines broad 



4. Zoster a. 



Flowers dioecious; fruit sagittate-cordate; leaves % to 2 lines broad . . . 



5. Phyllospadix. 



Leaves with spiny-toothed margins; pistil solitary and naked 



6. Naias. 



1. POTAMOGETON L. Pondweed. 

 Perennial herbs, commonly growing in still fresh waters, with 

 mostly alternate leaves in 2 ranks and membranous stipules more or 

 less united and sheathing. Spikes sheathed by the stipules in the bud, 

 in flower mostly raised on a peduncle to the surface of the water. 

 Flowers small, perfect. Sepals 4, rounded, concave, valvate in the 

 bud, short-clawed. Stamens 4, inserted on the claws of the sepals, 

 the anthers nearly sessile. Ovaries 4, becoming ovoid or roundish 

 drupelets. (Greek potamos, a river, and geiton, a neighbor, on 

 account of the aquatic habit. ) 



Stipules axillary and free from the leaf. 

 Floating leaves elliptical, submerged leaves lanceolate . . . 1. P. lonchiOs. 

 Leaves all submerged, 

 Ovate or lanceolate, many-nerved; spike 2 to 2% in. long . 2. P. lucens. 

 Linear, 1 to 3-nerved. 



Spike subcapitate; stem flattened; leaves not glandular 



3. P.pauciflorus. 



Spike interrupted or subcapitate; stem filiform; leaves often bi- 



glandular at base A. P. pusillus. 



Stipules adnate to the leaves or petioles; leaves all submerged, capillary . . . 



5. P. pectinatas. 



1. P. lonchites Tuckerm. Stems much branched, 3 to 6 ft. 

 long; floating leaves coriaceous, elliptical, 2 to 3£ in. long, less 

 than | to in. wide, the petiole usually longer than the blade; 



