TRIANDRIA. TRIGTNIA. 91 



123. PROSERPINICA. Z. 



Calix superior, S-parted, persistent. Corolla 

 0. JSPiit triquetrous, S-celled. 



Subaquatic; leaves alternate, under water pinnatifid 

 above lanceolate, serrate; flowers axillary, sessile. 



Species. 1. P. palustris. 2. pectmaia. Probably only 

 a variety of the preceding. 



A genus peculiar to the United States. 



