Jones: Flora of Illinois, 21. H\'drocharitaceae 45 



3. Fruiting pedicels thickened, spreading or recurved; sepals suborbicular, surround- 

 ing the mature fruit; lower flowers perfect, the upper staminate with 9-15 

 stamens 3. Lophoiocarpus 



3. Fruiting pedicels not thickened, ascending; sepals spreading or reflexed in fruit; 



lower flowers pistillate, the upper staminate with numerous stamens 



4. Sagittaria 



1. Alisma L. — Water-plantain 



A. subcordatum Raf. Ditches and margins of ponds, common. July- Aug. 

 [A. plantago-aquatica Am. auth., not L.} 



2. ECHINODORUS Rich. 



1. Scape erect, 10-30 cm. tall; stamens 12; style longer than the ovary; achenes 

 with a straight beak; shores of ponds, rare. June-July. [E. rostratus 

 Engelm.~\ E. cordifolius (L.) Griseb. 



1. Scape prostrate, proliferous; stamens about 21; style shorter than the ovary; 



beak of the achene incurved; swamps. June-July 



E. radicans (Nutt.) Engelm. 



3. LoPHOTocARPus T. Durand 



L. calycinus (Engelm.) J. G. Sm. Shallow water, rare. Peoria, Brendel. 

 July-Sept. 



4. Sagittaria L. — Arrowhead 



1. Leaves sagittate; stamens with glabrous filaments. 



2. Bracts of the inflorescence ovate, obtusish; beak of tht achene horizontal; 

 shallow water; July-Sept. Common Arrowhead S. latifolia Willd. 



2. Bracts lanceolate, acuminate; beak erect. 



3. Achenes 2 mm. long, with thin, unequal wings on both margins, the 



beak 0.5 mm. long; shallow water. July-Sept S. cuneata Sheld. 



3. Achenes 2.5-3 mm. long, with thick, equal wings; beak 1-2 mm. long; 



muddy shores, or in ditches, common. July-Sept 



S. brevhostra Mack. & Bush 



1. Leaves linear, lanceolate, or oval; filaments more or less glandular- pubescent. 

 4. Achenes 3 mm. long, the beak 1.5 mm. long; pedicels very short, the 



pistillate flowers nearly sessile; ditches or muddy shores; June-Sept 



S. rigidd Pursh 



4. Achenes 2 mm. long, the beak less than 1 mm. long; pedicels of the pistil- 

 late flowers equalling those of the staminate; shallow water. June-Sept. 

 S. graminea Michx. 



21. Hydrocharitaceae Aschers. — Frogbit Family 



1 . Leaves cordate, petioled 1. Limnobhim 



1 . Leaves neither cordate nor petioled. 



2. Leaves basal, ribbon-like, elongated, floating 2. Vallisneria 



2. Leaves small, whorled or opposite, sessile, pellucid, 1 -veined; stems elongated, leafy, 

 floating 3. Anacharis 



