894 



GRASSES OF IOWA. 



forest and prairie conditions. The leaves of these grasses are provided 

 with bulliform cells which cause their rolling up when the soil becomes 

 dry. Several grasses of this class are true bunch grasses, as Andropogon 

 scoparius (the bunches often consist of ioo or more culms), Dactylis 

 glomerata and Ely //ins robust us. These grasses may be divided into (a) 

 those occurring in forests and woodland, and (b) those occurring in open 

 prairie. The two communities sometimes merge into each other. In 

 most cases the communities are easily separated. 



Fig. 266. Wild Kice. Zizania aquatua. Found growing with Sagittaria, Phragmites 

 vulgaris and Acor us. Steamboat Rock. (Charlotte M. King, Photo.) 



Woodland: Diarrhena Americana (widely distributed and associ- 

 ated with Elymus striatus, Festuca nutans, and Melica mutica. The 

 latter though placed here prefers rather rocky, exposed places. Species 

 bordering woods and copses: Andropogon nutans, Elymus i irginicus, 

 Asprella hystrix and P annum macrocarpon. 



Prairies: The most conspicuous grass of the prairies is Elymus 

 robustus, which, grows to great heights, Andropogon scoparius, A. pro- 

 vincialis, Muhlenbergia Mexicana, Panicum virgatum, Sporobolus longi- 

 lolius, S. neglectuSj and S. vaginaeflorus. 



