280 



Lemnaceae Spirodela 



Lawrence E. The Lemnaceae of Indiana. Amer. Midland Nat. 18: 774- 



789. 1937.] 



Plants of this family are small in size and wholly aquatic, living on or 

 under the surface of the water. Anyone interested in the study of this 

 family of plants should read the "Lemnaceae of Indiana" by Lawrence E. 

 Hicks. All of my specimens have been studied by Prof. Hicks. The follow- 

 ing text has been copied from his paper and acknowledgment is hereby 

 made. 



Plants with roots and two reproductive pouches from each node. 



Each plant of a group with several roots growing out in a fascicle from the node; 

 plants 2.2-6.5 mm wide and 2.4-9.5 mm long, usually reddish below and with 

 a red eye spot (the node) above; dorsal surface of living specimens a glossy 

 green 794. Spirodela, p. 280. 



Each plant of a group with only one root 795. Lemna, p. 280. 



Plants without roots and with only one reproductive pouch from each node. 



Plants thick and globular 796. Wolffia, p. 281. 



Plants thin and straplike, usually submerged and attached in groups shaped like 

 rimless wheels 796A. Wolffiella, p. 282. 



794. SPIRODELA Schleid. 



1. Spirodela polyrhiza (L.) Schleid. GREATER DUCKWEED. Map 577. 

 Locally abundant throughout the state in lakes, ponds, swamps, ditches, 

 and sluggish streams. These plants are preyed upon by insects. 



N. S., Ont. to B. C, southw. to Fla., Tex., and Calif. ; also in Eu., Asia, 

 and tropical Amer. 



795. LfiMNA L. 



Plants feather-shaped with the basal portions of the long internodes narrowed into 



petiolelike stems, usually submerged 1. L. trisulca. 



Plants oval to oblong, without petiolelike stems, connecting plants appearing sessile, 

 usually floating. 

 Shape of plants symmetrical or nearly so. 



Plants deep green, thickish, convex on both surfaces, obscurely 3-veined, cavernous 

 throughout, appearing medium thick when pressed, sometimes reddish or 



purplish, especially below; margins thick 2. L. minor. 



Plants usually pale green, lower surface nearly flat, obscurely 1-nerved, cavernous 



in the middle portions only; membranous when dried; margins thin 



3. L. minima. 



Shape of plants unsymmetrical. 



Body of plant obliquely obovate, medium thick, usually deep green with some 

 reddish purple, distinctly 3-veined, cavernous throughout; root sheath with 



lateral wing appendages 4. L. perpusilla. 



Body of plant long-oblong, thin, pale green, obscurely 1-veined; root sheath unap- 

 pendaged; cavernous in the middle portions only 5. L. cyclostasa. 



1. Lemna trisulca L. SUBMERGED DUCKWEED. Map 578. Found com- 

 monly in ponds, shallow lakes, sloughs, and bogs, often growing beneath 

 floating species, preferring cold, shaded water. 



N. S., Ont. to B. C, southw. to Fla., Tex., and Calif. ; also in parts of Eu., 

 Asia, Africa, and Australia. 



2. Lemna minor L. Lesser Duckweed. Map 579. Throughout the state 



