Ev ^ 



CONTENTS 



Acknowledgments 368 



Environment 370 



Climate 370 



Temperature 370 



Precipitation 372 



Frost 372 



Wind 372 



Physiography and Geology 372 



Surficial Material 372 



Exposure 373 



Altitude 375 



Parallel Tributary' Valleys 375 



Environmental Conclusions 375 



X'egetation of Hill Prairies 375 



Phegley and Sampson Prairies 375 



Study Procedures 378 



Sizes and Shapes of Study Plots 379 



Method ot Counting Plant Units 380 



Density of Vegetation 381 



Grasses 381 



Plants Other Than Grasses 382 



Total Densities 383 



Ground Space of Plants 383 



Phegley Prairie 383 



Sampson Prairie 384 



Foliage Area or Crown Cover 384 



Available Space per Plant 386 



Numbers of Plant Species for \ arious Plot Sizes 387 



Sampson Prairie 387 



Phegley Prairie 387 



Frequenc>' of Occurrence of Species 389 



Sampson Prairie 389 



Phegley Prairie 390 



Frequency Values for Combinations of Species 390 



Species-Area Curve 391 



Summary of Pastured and Unpastured Prairies 392 



Vegetation Characters From Other Stands 392 



Presence 392 



Seasonal Aspect 393 



\'egetational History and Succession 393 



Annotated List of Hill Prairies 395 



East Dubuque to Grafton 396 



Along Rock, Sangamon, and Illinois Rivers 401 



Grafton to Cairo and Elsewhere in Southern Illinois 405 



Flor.\ of the Hill Prairies 413 



Annotated List of Species 414 



Geographical Relations of the Hill Prairie Flora 441 



Summary 441 



Literature Cited 444 



