206 IOWA ACADEMY OF SCIENCES. 



32. S. cristafa Eugelm. The type of this rare species 



was discovered in 1881, in a small lake, east of 

 Armstrong. The station has since been destroyed 

 but the plant occurs in several localities in 

 Minnesota. 



VALLISNERIACE^E. 



Philotria Raf. Ditch-moss. 



33. P. canadensis (Michx.) Britton. Rare in rivers and 



lakes. 

 Vallisneria L. Eel-grass. 



34. A. sjjiralis L. Rather frequent in lakes, but rarely 



seen in flower. 



POACE^. 



Andropogon L. Beard-grass. 



35. A. scoparius. Michx. Common on rather dry 



prairies. 



36. A. farcaius Muhl. {A provinciaUs Gray's Man.) 



Crow-foot grass; very common; a valuable species 

 for hay and pastures, but like most of our native 

 grasses, quickly destroyed by close grazing. 



SORGHASTRUM Nash. 



37. *S'. arenaccum (Michx.) Nash. {Chnjsopofion avena- 



ceus Michx.) Benth. {Sor(jhnin nutans Gray). 

 Common on prairies with the preceding species. 

 Stntherisma Walt. 



38. S. sanguiitale (L.) Nash. [Panicum sa)i<ju'tnalc L.) 



A worthless European species introduced in cul- 

 tivated and waste ground. 



3y. S. linearis (Krock.) Nash. {Panicmn (jlahrum Gme- 

 lin.) Common; banks of lakes and streams. 

 EcHiNOCHLOA Beauv. Barn-yard Grass. 



40. E. crus-galli (L.) Beauv. [Panicum crus-gaUi L.) 

 Introduced in cultivated and waste places. 



