100 naiadacejE. 



submerged leaves very thin, lanceolate, 4 to 12 in. long, rounded at 

 base or tapering into a petiole 1 to 4 in. long; stipules 1 to 4 in. long; 

 peduncles 2 to 3 in. long; spikes 1 to 2 in. long, densely fruited; 

 nutlets obliquely obovate, If to 2 lines long. 

 Streams: Kussian River southward to Santa Cruz; Sierra Nevada. 



2. P. lucens L. Stem branching below and often with masses of 

 short leafy branches at summit; leaves all submerged, thin, elliptical 

 to lanceolate or oblanceolate or the uppermost oval, many-nerved, 

 acute or acuminate, mucronate, often undulate-serrate, narrowed at 

 base to a short petiole or sessile, 2 to T in. long and f to If in. wide; 

 nerves 13 or fewer; stipules loose and spreading, sometimes very 

 broad; peduncles 3 to 6 in. long; spikes 2 to 2J in. long, very thick 

 cylindrical; nutlet IJ lines long, nearly as broad. 



San Francisco Peninsula. 



3. P. pauciflorus Pursh. Stems flattened, much branched, 1 to 

 3 ft. long; leaves all submerged, narrowly linear, 3-nerved or the 

 nerves obscure, 1 to 2 in. long, J to 1 line wide,, narrowed at base; 

 stipules small, white, becoming setose; peduncles more or less clavate, 

 about J in. long; spike subcapitate, few-flowered; nutlet 1 line long, 

 roundish or obliquely obovate, with a broad more or less undulate- 

 dentate keel. 



Still waters; near the coast. 



4. P. pusillus L. Stems flliform, branching, J to 1 ft. long; 

 leaves all submerged, narrowly linear or often nearly setaceous, 

 obtuse and mucronate or acute at apex, 1 to 3-nerved, with 2 glands 

 at base or rarely glandless, 1 to 3 in. long, |- to f line wide, sessile;, 

 stipules obtuse, becoming setose; peduncles flattened, slender, J to 3 

 in. long; spikes interrupted or capitate; nutlet obliquely elliptical, J 

 to 1 line long, curved and 2-grooved on the back, or sometimes with 

 3 distinct keels, beaked by a short style. 



Pools and ditches. Coast Ranges. 



5. P. pectlnatus L. Stems slender from a running rootstock, the 

 branches repeatedly forking, 1 to 8 ft. long; leaves capillary or 

 setaceous, often 1-nerved, 1 to 6 in, long; stipules J to 1 in. long, free 

 for half their length; peduncles filiform, 2 to 12 in. long; flowers in 

 distinct whorls on a spike J to 2 in. long; nutlets roundish or 

 obliquely obovate, IJ to 2 lines long, no middle keel on the back but 

 with obscure lateral ridges. 



Brackish water of tide sloughs or in ponds. 



2. RUPPIA- L. DiTCH-OKASS. 



Immersed aquatic herbs with long filiform forking' stems. Leaves 

 almost capillary, with a rather broad sheathing base. Peduncle of 

 the spadix axillary, at first very short and enclosed in the sheathing 

 spathe-like base of the leaf Spadices slender, each with two flowers 

 disposed hear together, rising to the surface when in anthesis. 

 Flowers perfect, entirely destitute- of perianth. Stamens 2, sessile 

 each anther consisting of 2 large and separate anther-cells. Pistils 



