BULLETIN 205, U. S. DEPABTMENT OF AGRICULTURE. 
Two genera of duckweeds lack roots. One of these ( Wolffia, fig. 2, 
e, f) contains the smallest flowering plants. These appear as green 
granules, one twenty-fourth of an inch or less in diameter, and are 
often abundant among other duckweeds or about the margins of 
lakes and ponds. When the hand is dipped into the water large 
numbers of the plants adhere to it. They look like coarse meal, 
except for their green color, and feel like it, so that a good name for 
them would be water meal. 
The other genus of rootless duckweeds ( WolffieUa) consists of strap- 
shaped plants (fig. 2, g, 7i) , narrowed at one or both ends. They are 
from one - fifth to 
three-fifths of an inch 
in length and com- 
monly cohere in ra- 
diate bodies or in 
large masses of less 
definite structure. 
Duckweeds are 
known also as duck's 
meat, water lentils, 
and seed moss. The 
latter term, in fact, is 
used in Arkansas to 
cover all components 
of the vegetation ' of 
the water surface. 
Besides duckweeds, 
this mass includes 
that green or red, vel- 
vety, mosslike plant, 
Azolla caroliniana, 
and the branching 
straplike liverworts, 
RiccieUa. Both of these are eaten by waterfowl along with the duck- 
weeds, but being less plentiful are of minor importance. 
DISTRIBUTION. 
Most of the species of duckweeds are wide ranging. Of the single- 
rooted kind (Lemna, fig. 2, c, d), 3 species occur throughout the 
United States, 2 others are confined to the southern part, and 1 to 
the eastern. The one many-rooted species (Spirodela, fig. 2, a, b), 
is of universal distribution. The granulelike rootless forms ( Wolffia, 
fig. 2, e, f), so far as known, are confined to the eastern half of the 
country, and the straplike rootless species ( WolffieUa, fig. 2, g, Ji) 
to the southeastern quarter. 
Pig. 2.— Duckweeds: 
b, Spirodela; c, d, Lcmna; c, f, Wolffia; g, h, 
Wolffiella. 
