ZANNICHELLIACEAE. 1 1 



1. P. natans L. Stems 1-1.5 m. long, simple or sparingly 

 branched; floating leaves thick, ovate-elliptic to lanceolate, rounded 

 or subcordate at base, 4-8 cm. long, mostly shorter than the petiole; 

 submerged leaves reduced to phyllodes or bladeless petioles; peduncle 

 as thick as the stem, 4-8 cm. long; spike dense, 4 cm. long; fruit 

 turgid, 4 mm. long, narrowly obovoid; nutlet pitted on the sides, 

 2-grooved on the back. 



Bear Valley, San Bernardino Mountains. Not known within 

 our limits. 



2. P. americanus Ch. & Sch. Stems 1-2 m. long, much branched; 

 floating leaves rather thin, elliptic, pointed at both ends, 5-10 cm. 

 long; submerged leaves linear-lanceolate, 10-15 cm. long, 4-20 

 mm. wide, rounded at base or tapering into a petiole; stipules 2-8 

 cm. long, free from the leaves; peduncles thickening upward, 4-6 

 cm. long; spikes dense, 2-4 cm. long; fruit 4 mm. long, obliquely 

 obovoid, sides smooth, 3-keeled on the back. (P.lonchiles. Tuckerm.) 



Occasional in ponds in the valley region. 



3. P. foliosus califomicus Morong. Stems 0.3-1 m. long, much 

 branched, flattened or winged; leaves 3-5 cm. long, 2 mm. wide, 

 3-nerved or sometimes 5-nerve(i toward the base; stipules free from 

 the leaves, small, white, becoming setose; peduncles 8-12 mm. long, 

 erect, clavate, flattened; spikes subcapitate, 6-12-flowered; fruit 

 lenticular or nearly orbicular, about 2 mm. long, 3-keeled on the 

 back, middle keel winged, sinuate-dentate, face strongly angled or 

 arched; style apical. (P. paticiflorus califomicus IVIorong.) 



Occasional in streams and irrigating ditches in the interior valleys. 

 June-September. 



4. P. pectinatus L. Stems 0.3-1 m. long, slender, much branched, 

 branches repeatedly forking; leaves setaceous, attenuate to the 

 apex, 1-nerved, often capillary and nerveless, 2-10 cm. long; stipules 

 half free, 1-2 cm. long, their sheaths scarious on the margins; 

 peduncles filiform, 4-10 cm. long; spike 1-4 cm. long; flowers in 

 whorls; fruit obliquely obovoid, about 4 mm. long, with two obscure 

 lateral ridges on the back; style straight or curved, facial. 



Common in streams and ponds. ^lay-August. 



2. RUPPIA L. 



Stems capillary, widely branched. Leaves all sub- 

 merged, very slender, attenuate, 1-nerved, with mem- 

 branous sheaths at the base. Flowers on a capillary 

 spadix-like peduncle, naked, perfect, consisting of 2 ses- 

 sile anthers, 2-celled, attached by the back to the 

 peduncle, having between them several pistillate flowers 

 with sessile peltate stigmas in 2 sets on opposite sides 

 of the rachis, the whole at first enclosed in the sheathing 

 base of the leaf; in development the peduncle elongates, 

 bearing the pistillate flowers at the end; fertilization 

 takes place at the surface, after which the peduncle coils 

 up. Fruit a small obliquely pointed drupe, pedicelled. 



