GENUS i. 



TAPE-GRASS FAMILY. 



105 



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 2>^"-3" long, 

 anthers i"-i}4" long. 3. P. Nuttallil. 



Leaves linear, rarely i" wide; staminate spathe i" lYz" long; anthers about J^" long. 



Leaves s"-io" long; sepals and petals 34 "-i" long. 

 Leaves 2 l / 2 "-^" long; sepals and petals H"-^4" long. 



i. Philotria canadensis (Michx.) Britton. Water-weed. 

 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. II. I : 85. 



1848. 

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



Stem slender, i-3i 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$"-5" 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, s"-7*" long; tube of 

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

 I" 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. 



2. P. angustifolia. 

 4. P. minor. 



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 Schweinitzii Planch. Ann. Sci. Nat. Bot. III. 



ii : 76. 1849. 

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



Sta. Colo. ioo:.is. 1906. 



Dioecious water plant; stem slender, flaccid, i-3i 

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

 about i" wide, rarely I" 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 i" long ; spathe of 

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

 ii'-4' long; sepals and petals elliptic, the former l"-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. PI. 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-3i long; 

 with the internodes often longer than the leaves. Leaves 

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

 lance-oblong, acute, 2*"-5" 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, f" 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. 



