A REVISION OF THE AMERICAN LEMNACEAE. 3l 
cleft opening which is irregularly torn by the developing 
floral organs. Pistil clavate; ovule solitary. Fruit sym- 
metrical, projecting about one-third beyond the margin of 
the frond; style short. Seed oblong-ovate; operculum 
prominent, directed forward, rounded ; ribs 12-15, uneven, 
high; seed coat thick, with many transverse striations.— 
Prolific, soon covering the surface of stagnant ponds. One 
of the most widely distributed species, occurring throughout 
our range.— Plate 2 B. 
The species is quite variable and in the vegetative stage 
very closely approaches the nongibbous resting stage of L. 
gibba. Striking examples of this are the Fink collections 
in Iowa (nos. 275, 399, 1894). 
Specimens examined from Nova Scotia (Fowler, 1868); Ontario (Gill- 
man, 1870); Vancouver Island (Macoun, 1887) ; Massachusetts (Trelease, 
1881); Connecticut (Eames, 1894); New York (Wright; Clinton, 1867) ; 
New Jersey (Austin, 1862; Leggett, 1868); Pennsylvania (Austin) ; 
Florida (Chapman, 1868; Canby, no. 17, 1869; Curtiss, no. 2695, 1881) ; 
Michigan (Bigelow, 1867; Gillman, 1870); Wisconsin (Blount; Trelease 
1887); Indiana (Simmons, 1895); Ilinois (Hall, 1861; Eggert, 1887; 
Thompson, no. 253, 1897) ; Minnesota (Sheldon, 1892); Iowa (Fink, nos. 
275, 899, 1894); Missouri (Engelmann, 1865; Bush, no. 528, 1896; Hen- 
ney and Thompson, 1896); Louisiana (Robbins, 1860; Hilgard, 1867); 
South Dakota (Rydberg, no. 1066, 1892); Nebraska (Webber, 1889; 
Clements, no. 2800, 1893; Rydberg, no. 1257, 1893); Indian Territory 
(Palmer, no. 316a, 1868); Colorado (Brandegee, 1876; Jones, no. 603, 
1878); New Mexico (Fendler, no. 1008, 1847; Bigelow, 1853); Idaho 
(Sandberg, no. 801, 1892); Utah (Jones, no. 16938, 1880, and no. 5321, 
1894); Nevada (Bailey, no. 1125, 1867; Watson, 1867); Washington 
(Henderson, no, 2534, 1892); Oregon (Hall, nos. 496, 497, 1871); Cali- 
fornia (S. B. and W.F. Parish, no 914, 1881; Thompson, 1896). 
+ + Fronds with a long stipe attached directly to the basal margin; 
young fronds projecting at right angles to the parent, forming a cross; 
fruit broadly oblong lenticular; rootcap acute pointed. 
Lemna trisutca Linn. Sp. Plant. 970. 1753. 
Fronds aerial and submerged, long persistent, usually 
many generations remaining attached and forming dense 
masses; oblong to oblong-lanceolate; slightly unsymmetri- 
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