42 ALISMACEAE 



3-5 mm. long : petals white : mature heads 3-4 mm. in diameter : achenes broadly and 

 obliquely obovate, barely 1 mm. long, black ; beak minute, sharp, oblique. 



In mud, Massachusetts to Ontario and Minnesota, Florida and Texas. Spring to fall. 



2. Echinodorus radicans (Nutt. ) Engelm. Leaf -blades ovate or oblong, 5-20 cm. 

 long, obtuse, undulate, truncate or cordate at the base ; petioles 1-7 dm. long : scapes 

 elongated, spreading or decumbent, creeping, 3-12 dm. long, often solitary : whorls of the 

 inflorescence remote : pedicels 3-12, unequal, 1.5-6 cm. long : bracts linear-lanceolate 

 from dilated bases : sepals ovate or orbicular-ovate, rather obtuse : petals white, about 

 6 mm. long : mature heads bur-like, 7-8 mm. in diameter : achenes cuneate, 2 mm. long ; 

 body 6-10-ribbed ; beak about J as long as the body. 



In ponds and swamps, Illinois and Missouri, to Florida and Texas. Spring and summer. 



3. Echinodorus cordifolius (L. ) Griseb. Leaf-blades various, lanceolate to broadly 

 ovate, 4-20 cm. long, obtuse, commonly truncate or cordate at the base ; petioles angled, 

 usually longer than the blades : scapes solitary or clustered, 1-5 dm. tall, surpassing the 

 leaves, simple or branched from the lower whorls of the inflorescence : pedicels 7-15 mm. 

 long, not very variable in length : bracts lanceolate or linear-lanceolate : sepals ovate, 

 rather acute : petals white, 4-6 mm. long, usually broader : mature heads bur-like, 4-6 

 mm. in diameter : achenes 2.5-3 mm. long ; body cuneate ; beak slender, fully ^ as long 

 as the body. [E. rostratus Engelm.] 



In ditches and swamps, Illinois and Missouri, to Florida and Texas. Spring and summer. 



3. LOPHOTOCARPTJS T. Durand. 



Annual or perennial acaulescent aquatic or marsh herbs. Scapes simple below the 

 inflorescence. Flowers in several whorls of 2-3 at the top of the scape ; upper staminate ; 

 lower pistillate. Stamens 9-15, hypogynous : filaments flattened, inserted at the base of 

 the receptacle. Pistils numerous on a convex receptacle. Style slender, oblique. 

 Achenes crowded together, crested or winged, more or less completely enveloped by the 

 calyx. Embryo horseshoe-shaped. 



Petioles 0.5-1.5 dm. long: leaf-blades less than 4.5 cm. broad : whorls of the inflorescence usually soli- 

 tary : mature fruiting heads 7-8 mm. in diameter. 1. L. depauperatus. 



Petioles 1.5-4 dm. long : leaf-blades over 4.5 cm. broad : whorls of the inflorescence 



2-6 : mature fruiting heads 10-15 mm. in diameter. 2. L. calycinus. 



1. Lophotocarpus depauperatus J. G. Smith. Leaves with petioles 0.5-1.5 dm. 

 long ; blades oblong, elliptic, oval or ovate, sometimes sagittate or hastate, 1-2 cm. wide 

 or the small basal lobes spreading to a width of 3-4 cm. and acuminate : inflorescence of 

 usually 1 whorl : mature fruiting heads 7-8 mm. in diameter: achenes cuneate, about 1.7 

 mm. long, each with a slender horizontal beak. 



On margins of ponds, Wisconsin, Illinois, Missouri and the Indian Territory. Summer and fall. 



2. Lophotocarpus calycinus (Engelm.) J. G. Smith. Leaves with petioles 1.5-4 

 dm. long ; blades hastate or sagittate, sometimes almost triangular or lunate, the basal 

 lobes often longer than the middle one, spreading to a width of 5-30 cm. and usually 

 acuminate: inflorescence of 2-6 whorls : mature fruiting heads 10-15 mm. in diameter: 

 achenes cuneate, 2-2.5 mm. long, each with a triangular horizontal beak. [Sagittaria culy- 

 cina Engelm.] 



In swamps 01 ponds, often submerged, South Dakota to Delaware, Louisiana and New Mexico. 

 Summer. 



4. SAGITTARIA L. 



Perennial acaulescent marsh or aquatic herbs, either erect or floating. Eootstock 

 irregularly thickened or tuber-bearing. Leaves various, usually differentiated into petioles 

 and blades, or reduced to phyllodes. Scapes sometimes greatly elongated, usually simple 

 below the inflorescence. Flowers monoecious or dioecious, in whorls of 3 near the top of 

 the scape, those of the upper whorls usually staminate. Staminate flowers with many 

 stamens : anthers 2-celled, opening by lateral slits : gynoecium wholly or partially sup- 

 pressed. Pistillate flowers with many distinct carpels : androecium wholly or partially 

 suppressed. Receptacle more or less convex. Achenes numerous, flattened, densely 

 crowded in globular heads. ARROW-HEAD. 



Sepals of the pistillate flowers reflexed or spreading, not accrescent. 

 Pedicels of the pistillate flowers much thickened, reflexed at maturity. 

 Filaments glabrous. 

 Scapes simple. 



Filaments about as long as the anthers : achenes with 3 undulate or slightly toothed crests. 



1. S. subulata. 



