LITERATURE CITED 
Barrows, H. H. 
(1) 1910. Geography of the Middle Illinois Valley. Bul. Ill. Geol. 
Surv., No. 15. 
Cannon, W. A., and Free, E. E. 
(2) 1917. The ecological significance of soil aeration. Science, new 
ser., 45 (No. 1156) : 178-180. 
County Soil Reports 
(3) Nos. 1-14, Univ. Ill. Agr. Exper. Station. 
Cowles, H. C. 
(4) 1899. The ecological relations of the vegetation of the sand 
dunes of Lake Michigan. Bot. Gaz. 27: 95-177, 167-202, 
281-308, 361-391. 
(5) 1900. Physiographic ecology of Chicago and vicinity. Bot. 
Gaz. 31: 73-108, 145-182. 
Gates, F. C. 
(6) 1912. The vegetation of the beach area in northeastern Illinois 
and southeastern Wisconsin. Bul. Ill. State Lab. Nat. 
Hist. 9: 255-372. : 
Gerhard, Frederic p 
(7) 1857. Illinois as it is, p. 288-247, 270-278. 
Gleason, Henry Allan i 
(8) 1909. Some unsolved problems of the prairies. Bul. Tor. 
Bot. Club, 36: 265-271. 
(9) 1910. The vegetation of the inland sand deposits of Illi- 
nois. Bul. Ill. State Lab. Nat. Hist. 9: 23-174. 
(10) 1912. A comparison of the rates of evaporation in certain 
associations in central Illinois. Bot. Gaz. 53: 478-491. 
Hart, Charles A., and Gleason, H. A. 
(11) 1907. On the biology of the sand areas of Illinois. Bul. Ill. 
State Lab. Nat. Hist., 7: 137-272. 
Harvey, E. M. 
(12) 1913. Evaporation and soil moisture on the prairies of Illinois. 
Trans. Ill. Acad. Sci., 6: 92-99. 
Hayden, Ada 
(13) 1919. The ecological foliar anatomy of some plants of a 
prairie province in central lowa. Amer. Jour. Bot. 6: 
69-85. 
(14) 1919. The ecologic subterranean anatomy of some plants of 
a prairie province in central Iowa. Amer. Jour. Bot. 6: 
87-104. 
Hopkins, Cyril G., Mosier, J. G., and Baur, F. C. q 
(15) 1916. Summary of Illinois soil investigations. Bul. Univ. 
fil. Agr. Exper. Sta., No. 193. 
