ALISMACEAE 9 



and sessile with stamens inserted on their base. Pistils one-celled and 

 one-seeded, forming hard nutlets in fruit. 



Leaves all submersed and similar. 1. P. foliosus. 

 Floating leaves different from the submersed. 



Submersed leaves linear. 2. P. SpirilluK. 



Submersed leaves lanceolate or broader. 3. P. LonchiUa. 



1. P. foliosus Eaf. Stems much branched, 2°-3° long : leaves linear, 

 1-3-nerved, \'-2' long, 1" vride : spikes 1-14-flowered : fruit roundish, 

 strongly keeled, the keel irregularly sinuate-dentate. — Hiffner's Lake 

 near Atherton. June-July. 



2. P. Spirillus Tuckerm, Larger floating leaves 9"-W long, 3"-8'' 

 •wide, longer than the slightly dilated petioles, strongly 7-14-nerved : 

 submersed leaves l'-2' long, J" wide : submersed spikes short-pedicelled, 

 capitately 4-10-flowered : fruit nearly 1" long, keeled on the back, with 

 4-5 teeth or wingless.— Ponds along the Little Blue Eiver between 

 Atherton and Glendale ; Grain Valley. May-July. 



3. P. Lonchites Tuokerm. Floating leaves pointed at both ends, 

 more or less elliptical in outline, 2'-4' long, 12"-20" wide : submersed 

 leaves reticulated, lanceolate, thin, 9'-13' long, &"-12" wide : spikes 

 V-i' long, cylindrical, heavily fruited : fruit keeled. — Common in a 

 pond near Sheffield, in Fish Lake, and in Hiffner's Lake. June-August. 



2. NAIAS L. 



Slender submerged aquatics with opposite spinulose toothed sessile 

 leaves. Flowers monoecious or dioecious, axillary, solitary and sessile. 

 Sterile flower consisting of a single stamen inclosed in a double perianth, 

 the pistillate of a single naked ovary. Fruit small and sessile. 



1. N. flexllis (Willd.) Eostk. & Schmidt. Delicate and slender with 

 minutely serrulate linear leaves about 1' long and V wide : sheaths 

 conspicuous, minutely toothed : seeds obscurely sculptured. — In the 

 pond north of Sheffield. Eare. June-July. 



FAMILY 11. ALISMACEAE DC. 



Marsh herbs with racemose-paniculate flowers on scapes. Petals and 

 sepals three each, the former white. Stamens six or more. Ovaries 

 numerous, one-celled, one-ovuled. Fruit an achene. Eoots fibrous. 

 Leaves numerous, all radical, and long-petioled. 



Flowers perfect. 



Stamens six, leaves lanceolate. 1. Altsma. 



Stamens twelve, leaves usually cordate. 2. E(5HInodoeus. 



Stamens 9-15, leaves sagittate. 3. Lophotocaepus. 



Flowers not perfect. 4. Sagittakia. 



