GENUS I. 



TAPE-GRASS FAMILY. 



10 = 



Leaves oblong or ovate-oblong, mostly obtuse; staminate flowers unknown. i. P. canadensis. 



Leaves linear or oblong, acute ; hermaphrodite flowers unknown. 



Leaves oblong or linear-oblong, i"-i l / 2 " wide; spathe of the staminate flowers 



long. 

 " long. 



Water-weed. 



II. i : 85. 



anthers i"-iJ4" long. 



Leaves linear, rarely i" wide; staminate spathe 

 Leaves s"-io" long; sepals and petals $4"-i 

 Leaves 2j^"-4" long; sepals and petals Yz"- 



i. Philotria canadensis (Michx.) Britton. 

 Fig. 248. 



Elodea canadensis Michx. Fl. Bor. Am. i : 20. 1803. 

 Elodea latifolia Casp. Jahrb. Wiss. Bot. i: 467. 1858. 

 ?Anacharis canadensis Babingt, Ann. & Mag. Nat. Hist. 



1848. 

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



Stem slender, i-3i long, usually with short intemodes. Leaves 

 verticillate in 3*3 or 4's, or the lower ones in 2's, sessile, oblong 

 or ovate-oblong, usually obtuse, 2j"-s" long, i"-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%" long; tube of 

 the hypanthium 2' -4' long; sepals and petals elliptic, obtuse, about 

 3" long; stamens usually 3, rarely 4-6, or reduced to mere fila- 

 ments; anthers oblong, nearly sessile; stigmas 3, spreading, pur- 

 plish, emarginate about equaling the petals and sepals. 



In ponds and slow streams, Quebec to Virginia and Minnesota. 

 Naturalized in Europe. Called also Choke Pondweed. 



long; anthers about 



3. P. 



Yt"-j>" long, 

 Nuttallii. 

 Ions'. 



angnstifolia. 

 minor. 



i 



2. Philotria angustifolia (Muhl.) Britton. 

 Narrow-leaved Water-weed. Fig. 249. 



Serpicula verticillata angustifolia Muhl. Cat. PI. Am. 



Sept. 84. 1813. 



^Serpicula occidentalis Pursh, Fl. Am. Sept. 33. 1814. 

 ?Apalanthe Schweinitsii Planch. Ann. Sci. Nat. Bot. III. 



ii : 76. 1849. 

 Philotria angustifolia Britton ; Rydb. Bull. Agr. Exp. 



Sta. Colo. 100 : 15. 1906. 



Dioecious water plant; stem slender, flaccid, i-34 

 long. Leaves in 3's or 2's, sessile, linear, 5"-io" long, 

 about i" wide, rarely f" wide, acute; spathe of the 

 staminate flowers i"-ij" long, sessile, ovoid; sepals 

 and petals elliptic or oval, the former about i" long, 

 the latter smaller ; anthers about \" long ; spathe of 

 the pistillate flowers tubular, i"-i" long; hypanthium 

 ij'~4' long; sepals and petals elliptic, the former |"-i" 

 long; stigmas 2-cleft. 



In streams New York and Pennsylvania to Florida. 



3. Philotria Nuttallii (Planch.) Rydb. Nuttall's 

 Water-weed. Fig. 250. 



Serpicula verticillata Muhl. Cat. PL Am. Sept. 84. 1813. 



Not S. verticillata L. 1781. 

 Anacharis Nuttallii Planch. Ann. & Mag. Nat. Hist. II. i : 



85. 1848. 

 Philotria Nuttallii Rydb. Bull. Torrey Club 35: 461. 1908. 



Dioecious water-plant; stem slender, i-3$ long; 

 with the intemodes often longer than the leaves. Leaves 

 usually in 3's or the lower ones in 2's, sessile, oblong or 

 lance-oblong, acute, 2i"-s" long, i"-ii" wide, finely 

 serrulate ; spathe of the staminate flowers ovoid, sessile, 

 2*"-3" long; flower without a tube; sepals and petals 

 oblong, the former scarcely exceeding the oblong an- 

 thers, which are i"-ii" long; sheath of the pistillate 

 flowers about 5" long, 2-cleft ; tube of the hypanthium 

 2'-6' long; sepals and petals elliptic, I" long; filaments 

 rudimentary; stigmas slightly exceeding the petals, 

 2-cleft at the apex. 



In slow streams and ponds, New York to Virginia. This 

 figure was used for P. canadensis in our first edition, formerly confused with this species. 



