106 ILLINOIS STATE ACADEMY OF SCIENCE 



3. Cowles, H. C: The plant societies of Chicago and vicinity. Bulletin 



No. 2, The Geographic Society of Chicago. 1901. 



4. Fuller, G. D., and P. D. Strausbaugh: On the forests of La Salle 



County, Illinois. Trans. Ill State Acad. Sci. 22:246-272. 1919. 



5. Kurz, H.: Hydrogen ion concentration in relation to ecological 



factors. Bot. Gaz. 76:1-29. 1923. 



6. Thone, F.: Ecological factors in region of Starved Rock, Illinois. 



Bot. Gaz. 74:345-368. 1922. 



7. Thone, F. : Advantages of river canyons for ecological study. 



Trans. 111. State Acad. Sci. 15:202-207. 1922. 



8. Thone, F.: Evaporation rates on rock canyon walls. Bot. Gaz. 76: 



419-424. 1923. 



