446 Illinois Natural Historv Survey Bulletin Vol. 26, Art. 5 



1931. A preliminary vegetation map of Illinois. 111. Acad. Sci. Trans. 23(3 ) :204-17. 

 1945. Flora of Illinois. [A review of a book with that title.] Science, n.s., 102(2656) : 542-3. 

 1949. Minimum areas for different vegetations: Their determination from species-area 

 curves. III. Biol. Monog. 20(3):1-129. 



Vestal, A. G., and H. Bartholomew 



1941. Prairie of loess bluffs of the Illinois River. (.Abs.) Ecol. Soc. Am. Bui. 22(4) :41. 



Vestal. Arthur G., and Mary Frances Heermans 



1945. Size requirements for reference areas in mixed forests. Ecology 26(2) : 122-34. 



Woodard, John 



1924. Origin of prairies in Illinois. Hot. Gaz. 77(3) :241-61. 



Worthen, A. H. 



1868. Geological survey of Illinois. Vol. 3. Geology and palaeontology. [Illinois Geological 

 Survey, Springfield.] 574 pp. 



