( 324 ) 
Ovaries 4, styles 0.—2¢. Jointed aquatics. In- 
florescence pedunculate; spikes axillary. 
1. P. watans L. Floating leaves coria- 
ceous; submerged leaves filiform. — Marine 
Hospital. Lake Merced. Taylorville. Sum- 
mer. 
2. P. tucens L. Leaves. uniform, lanceo- 
late.—Mission Dolores. Lake Merced. Sum- 
mer. 
3. P. pauciFLoRUS Pursh. Leaves linear 
with distinct stipules—Ocean Lake. Sum- 
mer. 
4. P. pectinatus L. Leaves linear, sti- 
pules united with the sheathing base of the 
leaf.—Common. Summer. 
OrvEr 2. CENTROSPERMA. Perigonium 
0. Ovules basilar. 
Family 1. NAIADACEZ. 
Flowers diclinous. Ovary I, 1-celled, 1- 
ovulate. Fruit a nutlet. 
1, Lilea HBK. 
Flowers monecious. ¢, spicate, 1-bracteate, 
monandrous, sometimes mingled with ? flow- 
ers. ? flowers partly spicate and 1-bracteate; 
partly solitary, axillary and without bracts: 
Styles of the upper ? flowers short, of the 
lower elongate; stigmas capitate.—@©. Aqua- 
tic. Leaves radical, terete, sheathing at base. 
