12 



Tidestrom, 1. 1910. Notes on Peltandra, Rafinesque. Rhodora 12: 47-50. 



Wilson, K. A. 1960. Genera of Arales in the southeast United States. 

 J. Arnold Arbor. 41: 47-72. 



LEMNACEAE 



1. Plants lacking roots (fig. 5A,B,C,D). 



2. Fronds 1.5 mm or less long, thick, globular or ellipsoidal (fig. 

 5A,B,C). 

 Wolffia 



2. Fronds 6-8 mm long, thin, slender, elongate, sickle-shaped (fig. 5D). 



Wolffiella 



1. Plants with roots (fig. 5E, 6). 



3. Frond with two or more roots, solid reddish-purple on the 

 underside, upper surface with 3-11 nerves (fig. 5E), 



: Spirodela 



3. Frond with a single root, green or slightly purple on the 

 underside, upper surface with 1-3 nerves (fig. 6). 

 Lemna 



Wolffia (Water-meal) 



Minute floating plants of quiet waters, usually in small ponds, 

 river backwaters, and ditches; rootless; fronds greatly reduced; flowers 

 rare, consisting of one pistillate and one staminate (with a single 

 stamen) flower enclosed in a sac-like spathe; firuit a utricle; vegetative 

 reproduction extensive. 



This genus contains the smallest known flowering plants. The 

 species are extremely difficult to identify, especially if allowed to dry. 

 Every effort should be made to identify Wolffia while material is fresh 

 or is preserved in liquid, not dried. 



Key to Species 



1. Frond globular (fig. 5A), not dotted, some plants below surface 

 under crowded conditions. 



1. W. Columbiana 



1. Frond ellipsoidal (fig. 5B,C), dotted, floating on surface when 

 crowded. 

 2. Upper suface flattened (fig. 5B). 



2. W. borealis 



