CHAPTER III. 



The Ecological Distribution of Iowa Grasses. 



GENERAL DISCUSSION. 



Plants are dependent on their surroundings. The nature of the soil, 

 such as mechanical and chemical conditions, as well as climate are factors 

 of the greatest importance in the life relations of plants. Naturally in 

 a prairie state like Iowa there is less variation than in a region broken by 

 mountain chains, lakes and bogs. It will not be necessary to treat in 



Fig. 257. Approach to Ledges, Boone county, Iowa. Carboniferous sandstone . Danthonia spicala, Cladonia, 

 Polytrtchum on the bare slopes, Bromus purgans, Festuca tenella and Asprella Hystrix in woods. Eragrostis 

 cap Maris on sandy banks; E, Purshii in sandy bottoms. (J. A. Caughey, Photo.) 



