BULLETIN 205, U. S. DEPARTMENT OF AGRICULTURE. 



Two genera of duckweeds lack roots. One of these ( WolMa, 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 ( Woljfiella) consists of strap- 

 shaped plants (fig. 2, g, h), 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, 

 Ricciella. 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, $), 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 ( Woljfiella, fig. 2, g, Ti) 

 to the southeastern quarter. 



Fig. 2. 



-Duckweeds: a, b, Spirodela; c, d, Lemna; e, f, Wolffia; g, h, 

 WolffieUa. 



