214 LEMNACEAE 



Tertiary o: Cretaceous, perhaps at Woodbridge, N. J., not other- 

 wise known: Older formations, common, increasing northward. 

 Not south of the moraine. 117-186 days. Sea level-1,933 ft. 



4. Spathyema Raf. 

 1. S. foetida (L.) Raf. In swamps and wet soil: N. S. to Ont., 

 Minn., N. Car. and Iowa. 



Throughout the range except in the pine-barren region of N. J. 

 and L. I. where it is rare and local or often wanting. 



5. Orontium L.* 

 1. O. aquaticum L. In swamps and ponds: Mass. to Pa., Fla. 

 and La., mostly near the coast. 



Conn. Common in the coastal counties, decreasing northward. 

 N. Y. L. I. and up the Hudson Valley to Orange Co. 

 N. J. Nearly throughout, increasing southward and in the coastal 



counties. 

 Pa. Pike, Monroe, Northampton, Lehigh, Delaware and Chester 

 counties. 



6. Acorus L. 

 1. A. Calamus L. In swamps and along streams: Nov. Scot, to 

 Ont., Minn., La. and Kan. Also in Europe and Asia. 

 Common throughout the range, rare in the pine-barrens. 



LEMNACEAEf 



Thallus with 1-00 roots. 



Roots several. I. Spirodela. 



Root solitary. 2. Lemna. 



Thallus rootless. 3- Wolffia. 



I. Spirodela Schleid. 

 I. S. polyrhiza (L.) Schleid. In still water: Nov. Scot, to Brit. 

 Col., S. Car., Tex., northern Mex. and Nev. 



Not uncommon as a ditch or pond plant in most parts of our 

 range except the pine-barrens. 



2. Lemna L. 



Thalli long stipitate, 5 mm. long or more. I. L. trisulca. 

 Thalli short stipitate or sessile, mostly less than 5 mm. long. 

 Spathe open. 



Thalli 1 -nerved or nerveless. 2. L, cycloslasa. 



Thalli 3-nerved; root cap cylindric. 3. L. perpusilla. 



Spathe sac-like. 4- L. minor. 



* See footnote page 76. 

 T See footnote, page 76. 



