no UNIVERSITY OF MISSOURI STUDIES [^5^ 



2i8. A. Dracontium (L.) Schott. \_M. Dracontium (L.) 

 Small]. Green dragon. 

 Rich hillsides; infrequent. 

 Maine to Minnesota; Florida to Louisiana. 



Family 13. LEMNACEAE Dumort. Duckweed family. 



73. SPIRODELA Schleid. Duckweed. 



2ig. S. polyrrhiza (L.) Schleid. 



Floating on ponds, or occasionally rooting on muddy 

 shores or the bottoms of dried-up puddles. 



All temperate and tropical lands. 



74. LEMNA L. Duckweed. 



220. L. Valdiviana Philippi [Z. cydostasa (Ell.) Chev.]. 

 Floating on ponds; occasionally fruiting in autumn. 

 Massachusetts and Florida to California and Mexico: 



South America. 



221. L. minor L. Little duckweed. 

 Floating on ponds; common. 

 Cosmopolitan. 



75. WOLFFIA Horkel. 



222. W. papulifera Thompson. 

 Ponds; the typical station. 

 Kennett and Columbia, Missouri. 



Order 9. FARINOSALES. 



Family 14. COMMELINACEAE Reichenb. Spiderwort 

 family. 



76. OOMMELINA L. Day-flower. 



223. 0. nudiflora L. 



Alluvial banks of Brushwood lake. 



New Jersey to Missouri; Florida and Texas to Para- 

 guay. 



