NAIADACEiE. 99 



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

 Id 2's, broadly tongue-shaped, | to IJ lines wide, IJ to 3| lines long, 

 cavernous throughout the lower central portion; reproductive pouch 

 triangular. 



Irrigation canals, Kero Co., Thompson. 



8. NAJADACE^. Pondweeo 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. Potamogeton. 



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 on the side of a linear spadix; marilime. 

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



4. ZOSTERA. 



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. Po.vdwbed. 

 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, vahate 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 fi-ee from the leaf. 

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

 Leaves all submerged. 

 Ovale or lanceolate, many-nerved; spike 2 to 2>^ in. long . 2. P.lucens. 

 Linear, 1 to 3-nerved. • 



Spike siibcapitate; stem flattened; leaves not glandular 



3. P.paudJJoj-us. 

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



glandular at base 4. P. pusiUus. 



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



5. P. pectiTiatiis. 



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

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

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



