84 UNIVERSITY OF MISSOURI STUDIES [226 



Family 8. ALISMACEAE DC. Water plantain family. 



18. ALISMA L. Water plantain. 



27. A. PlantagO L. [A. Platilago-aquatica Auct.: A. sub- 

 cordatum Raf.]. 



About ponds and streams, and in swales and swamps. 

 North America: Europe and Asia. 



19. LOPHOTOCARPUS Durand \LOPHIOCAR- 

 PUS Miq.: SAGITTARIA L.]. 



28. L. calycinus (Engelm.) J. G. Smith {Lopkiocarpus 

 calycinus (Engelm.) Micheli: S. calycinus Engelm.]. 



Muddy margins of ponds, often in dense masses. 

 Almost transcontinental. 



20. SAGITTARIA L. Arrowhead. 



29. S. variabilis Engelm. \S. latifolia Willd.]. Common 



ARROWHEAD. 



Muddy margins of ponds and streams; very variable in 

 foliage, some forms connecting closely with the preceding. 

 Transcontinental. 



30. S. platyphylla (Engelm.) J. G. Smith. 



Stagnant waters near the covered bridge over Roche 

 Perche creek. 

 Alabama to Missouri and Texas. 



Family 9. HYDROCHARITACEAE Aschers. Frog's-bit 

 family. 



21. ELODEA Michx. \PHILOTRIA Raf.: UDORA 

 Nutt.]. Water thyme. 



31. E. minor Engelm. {P. minor (Engelm.) Small: U. 

 CanadcTisis mi?ior Engelm.]. Waterweed. 



In ponds; local. 



Minnesota and Missouri to Tennessee and Arkansas. 



