ARTICLE VII. ON THE BIOLOGY OF THE SAND AREAS OF 



ILLINOIS. BY CHARLES A. HART AND HENRY ALLAN page 



GLEASON. (1 Map and 15 Plates.) January, 1907 137-272 



Introduction 137 



Part I. Glacial Geology and General Characters of the Illinois Sand 



Areas, especially those of Western Illinois. By Charles A. Hart. . 139-148 



Glacial Geology 139 



Topography : General 144 



The Surface Sands 145 



Other Sand Areas 146 



Part II. A Botanical Survey of the Illinois River Valley Sand Region. 



By Henry Allan Gleason 149-194 



Introductory 149 



Ecological Factors 149 



The Plant Associations 15 7 



The Bunch-grass Association 158 



The Blow-sand Association 162 



The Blowout Association 167 



Reversion to Bunch-grass 169 



The Black-jack Association 171 



Some Adaptations of the Plants to the Environment 178 



List of the Plants observed 181 



Phytogeographical Relationships of the Flora 189 



Part III. Zoological Studies in the Sand Regions of the Illinois and Mis- 

 sissippi River Valleys. By Charles A. Hart 195-267 



General Features 195 



The Localities visited 197 



Geographical Distribution of the Species 199 



Sand as a Factor of Animal Environment 208 



The Relation of Sand and Climate to Insect Coloration 211 



Local Distribution of Species in the Sand Areas. The Insect Associa- 

 tions 220 



Annotated List of Species 227 



Systematic Notes 259 



Bibliography 268 



ARTICLE VIII. ON THE LOCAL DISTRIBUTION OF CERTAIN 



ILLINOIS FISHES: AN ESSAY IN STATISTICAL ECOLOGY. page 



BY S. A. FORBES. (15 Maps and 9 Plates.) April, 1907 273-303 



Introductory 273 



Associative Relationships among the Etheostomince 275 



The Method of the Investigation 276 



Coefficients of Association 277 



Discussion of Associative Tables 280 



Typical and Non-typical Darters 281 



Sufficiency of the Collections 282 



Relations to Physical Environment 283 



Equalization of the Data 283 



