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 em. 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 1 as long as the body. 
In ponds and swamps, Illinois and Missouri, to Florida and Texas. Spring and summer. 
3. Echinodorus cordifdlius ( 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 3 as long 
as the body.  [ E. rostratus Engelm. ] 
In ditches and swamps, Illinois and Missouri, to Florida and Texas. Spring and summer. 
3. LOPHOTOCARPUS 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 em. 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 em. 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 caly- 
cina Engelm.] 
Santis swamps or ponds, often submerged, South Dakota to Delaware, Louisiana and New Mexico. 
er. 
4. SAGITTARIA L. 
Perennial acaulescent marsh or aquatic herbs, either erect or floating. Rootstock 
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. 
Seapes simple. 
Filaments about as long as the anthers: achenes with 3 undulate or slightly Lesen crests. 
1. S. subulata. 
