FIELD BOOK OF PONDS AND STREAMS 



Fig. 68. — Ivy-leaved duckweed, Lemna triscula. 



marshes. Frequent. Blooms in June-August. Rare near 

 the Atlantic coast but otherwise generally distributed over 

 the United States. 



Lesser duckweed, Lemna minor. — In spite of their small 

 size these duckweeds (!?ig. 69) also form green blankets on the 



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Fig. 69. — Lesser duckweed, Lemna minor. 



water. The thallus is but a small fraction of an inch long, 

 has but one root, and i to 5 simple veins. 



Occurrence. — Very common, floating on quiet waters of 

 ditches and ponds, sometimes on wet mud. June-August. 

 Throughout North America except in extreme north. 



84 



