[Elodea Michx. Fl. Bor. Am. 1: 2c. 1803. Not Elodes Adans. 1763.] Stems submerged, elongated, branching, leafy. Leaves opposite or whorled, crowded, 1-nerved, pellucid, minutely serrulate or entire. Flowers dioecious or polygamous, arising from an ovoid or tubular 2-cleft spathe. Perianth 6-parted, at least the 3 inner segments petaloid. Staminate flowers with 9 stamens, the anthers oblong, erect. Ovary 1-celled with 3 parietal placentae. Stigmas 3, nearly sessile, 2-lobed. Fruit oblong, coriaceous, few-seeded. [Name from the Greek, referring to the leaves, which are often whorled in three's.] About 10 American species. Type species Elodea canadensis Michx.

1. Philotria Canadensis (Michx.) Britton. Water-Weed

Fig. 248

Elodea canadensis Michx. Fl. Bor. Am. 1: 20. 1803. Elodea latifolia Casp. Jahrb. Wiss. Bot. I: 467. 1858. ?Anacharis canadensis Babingt, Ann. & Mag. Nat. Hist. II. I: 85.

1848. Philotria canadensis Britton, Science II. 2: 5. 1895.

Stem slender, 1° -3 1/2° long, usually with short internodes. Leaves verticillate in 3's or 4's, or the lower ones in 2's, sessile, oblong or ovate-oblong, usually obtuse, 2 1/2"-5" long, 1"-2" wide, minutely serrulate; staminate flowers unknown; flowers in the typical American form usually hermaphrodite, in the European (Anacha-ris Alsinastrum), pistillate; sheath tubular, 5"-7 1/2" long; tube of the hypanthium 2'-4 "long; sepals and petals elliptic, obtuse, about 3/4" long; stamens usually 3, rarely 4-6, or reduced to mere filaments; anthers oblong, nearly sessile; stigmas 3, spreading, purplish, emarginate about equaling the petals and sepals.

In ponds and slow streams, Quebec to Virginia and Minnesota. Naturalized in Europe. Called also Choke Pondweed.