32 MISSOURI BOTANICAL GARDEN. 
cal and frequently a little falcate; 2-3 mm. wide by 5-10 
mm. long; without papules of any kind; converging ter- 
minal margins serrate and commonly fluted; apex acute; 
base hastate in the young fronds, in the older ones attenu- 
ated into a flat stipe about .5 mm. wide by 4-13 mm. long; 
proliferous from both pouches. Aerial fronds cavernous 
throughout the central portion, shorter stipitate and less 
persistent. Submerged fronds longer, more persistent, 
thinner and with long twisted stipes. Roots frequently 
absent; rootsheath soon disappearing. Seed prominently 
12-15 ribbed with numerous transverse striations. —Prolific. 
This is a cosmopolitan species of very wide distribution, 
adapting itself to much colder temperature than any other 
species; not infrequently a hardy perennial. Common in 
springs and running water throughout our range.— Plate 
2C. 
Specimens examined from Saskatchewan (Bourgeau, 1857-58); Onta- 
rio (Fowler, 1881); Vancouver Island (Macoun, 1887); Massachusetts 
(Boott, 1859 and 1867); New York (Clinton; Austin; Britton, 1892); New 
Jersey (Austin, 1866); Michigan (Bigelow, 1865; Gillman, 1871); Wis- 
consin (Hale; Lapham); Illinois (Engelmann, 1838; Hall, 1861); Minne- 
sota (Ballard, 1893); Iowa (Hitchcock; Evermann, 1893); Missouri 
(Bush, no. 1495, 1886 and no. 536, 1896; Steadman, 1896); Arkansas, 
(Blankinship, 1888); Nebraska (Hayden, 1853; Webber, 1889; Williams, 
no. 7, 1890; Rydberg, no. 1397, 1893); Texas (Wright, no. 674; Schott, 
1855-56; Mexican Boundary Survey, no. 1410, 1855-56) ; Wyoming (Rose, 
no. 401, 1893; Nelson, no, 2284, 1896; Adams on U. 8. Geol. Survey, 
1871; Knowlton, 1887,— the last two from Yellowstone National Park); 
Colorado (Brandegee, 1881); New Mexico (Wright, no. 1890, 1851-52; 
Fendler, no. 1007, 1874); Utah (Watson, no, 1123, 1869; Ward, no. 594, 
1875; Jones, no. 6019, 1894); Nevada (Stretch, 1865; Watson, no, 1123, 
1868); Arizona (Palmer, no. 531, 1890); Oregon (Howell, 1879); Cali- 
fornia (Redfield, no. 8062, 1872; Austin, 1878; Lemmon, 1879), 
** Spathe open; ovule solitary, obliquely orthotropous with the 
micropyle inclined toward the apex of the frond; stipe attached to the 
basal margin. 
+ Frond 38-nerved; rootsheath with lateral longitudinal wing ap- 
pendages; rootcap long, cylindrical, straight, sharp-pointed. 
++ Fronds obliquely obovate to oblong-obovate, thick, nerves 
obscure, 
12 
