36 MISSOURI BOTANICAL GARDEN, 
Trelease, 1895; Widmann, 1895); Arkansas (Engelmann, 1885; Eggert, 
1892); Texas (Lindheimer, 1847-48); Wyoming (Rose, no. 401, in part, 
1893); New Mexico (Wright, no. 1891, 1851); Utah (Jones, 1880 and 
no. 5983g, 1894); Nevada (Watson, no, 1124, 1868; Coville, 401, 1891); 
Arizona (Palmer, 1865; Coues and Palmer, no. 451, 1865); California 
(Bigelow, 1853-54; Bolander, no. 2662, 1866; Orcutt, 1883-—a very 
large form; Henney, nos. 107, 113b, 1896), 
++++ Fronds thicker, with a row of papules along the midnerve; 
rootcap slightly curved, cylindrical, with bluntly rounded apex. 
Lemna minIMA Philippi, Linnaea. 33: 239. 1864. Lemna 
platyclados Hglm. Engler’s bot. Jahrb. 213: 298. 
Jan. 1895. 
Fronds solitary or cohering in groups of 2-4, commonly 
2; symmetrical or with stipe scar but little to one side 
of the median line; oblong to elliptical; .9-2.7 mm. wide 
by 1.5-3.9 mm. long; apex rounded; lower surface flat or 
slightly convex, upper surface slightly to prominently con- 
vex, with thin margin entirely around the frond; cavern- 
ous in the middle portion only; commonly nerveless. 
Rootsheath thin, cylindrical. Rootcap usually short, rarely 
perfectly straight. Pistil short clavate, with concave stig- 
ma. Seed oblong, pointed, about 16-ribbed, with many 
transverse striations.— An American species occurring in 
the south and west parts of our range, from there south 
into South America.— Plate 3D. 
This spécies seems to have at least two fairly well-defined 
stages in its growth. The first may be termed the normal 
or more constant, for in it the fronds are uniformly very 
small (averaging 1.1 mm. wide, by 1.7 mm. long) and 
strikingly convex on the upper surface and of a straw 
yellowish or sometimes pale green color. The second is 
more variable in its habits and is characterized chiefly by 
larger sized, thinner green colored fronds, and more vigorous 
growth throughout. This answers perfectly Hegelmaier’s 
description of Lemna ( Valdiviana var.?) platyclados. 
The fronds readily change from one form to the other. 
Specimens examined from Georgia (Ravenel, 1881); Florida (Curtiss, 
no, 4543, 1894); Kansas (Cragin, 1884); Wyoming (Forwood, 1882); 
16 
