Jones: Flora of Illinois 



GRAND PRAIRIE DIVISION 



I'he term is applied to the eastern portion ol Illinois, and includes 

 all the area of recent or Wisconsin glaciation which is for the most 

 part treeless. This area has the youngest soils of the state, in which 

 leaching of dissoKed materials has not progressed to any great extent. 

 Characteristic prairie-plants, including Silphium terehinthinaceum, 

 Eryngium yuccifolium, Sorghastrum nutans, Andropogon furcatus, 

 and Sporobolus heterolepis, are frequent in these areas of black prairie 

 soil. The morainal country of Lake and McHenry counties is hilly, 

 and was formerly extensively forested. Small tracts of timber still 

 remain. Quercus macrocarpa is one of the conspicuous trees. Tilia 

 americana and Quercus rubra are frequent in drier habitats. Many of 

 the lower areas are occupied by marshes, bogs, and lakes, and in these 

 places colonies of Larix laricina are to be found. 



The counties near Lake Michigan contain a number of northern 

 species, including Larix laricina, Pinus banksiana, Scheuchzeria amer- 

 icana, Carcx aurca, Eriophorum angustijolium, Betula pumila, Ribes 

 liirtellum, Shcpherdia canadensis, Cornus canadensis, Andromeda 

 glaucophylla, and Chamaedaphne calyculata. The beach area of Lake 

 Michigan has numerous sand-ridges and dunes, with intervening sand- 

 prairies and sloughs. Several species are peculiar to this area, such as: 

 Juniperus canadensis, J. horizontalis, Ammophila breviligulata, Cal- 

 amovilfa longifolia, Salix adenophylla, Cakilc edentula, Potentilla 

 anserina, Prunus pumila, Lathyrus maritimus, Chamaesyce polygoni- 

 folia, Arctostaphylos uva-ursi, and Artemisia caudata. 



WESTERN DIVISION 



This division includes most of the western part of Illinois. Much of 

 the area is covered by relatively old glacial drift (lUinoian) with recent 

 deposits of loess. These prairie areas contain several xerophytic western 

 species, including Boutcloua gracilis, Stylisma pickeringii, Lesquerella 

 argentea, Amorpha canescens, Opuntia rafinesquii, and Synthyris bullii. 

 Areas of lower elevation include prairie sloughs. Southwest of the 

 Grand Prairie, and west of the Illinois River, more than half the 

 area is occupied by forest, and only a few flat upland prairies of fair 

 size, such as the Bushnell and Carthage prairies occur. This condition 

 has been brought about by the extensive dissection of the country near 

 the larger rivers. 



jo DAVIESS HILLS 



The Driftless Area in Jo Daviess County has served as a refuge for 

 preglacial plants. At the present time there are several species of lim- 

 ited distribution within the state, including Adoxa moschatellina, 

 Dodecatheon amethystinum. Primula mistassinica. Ranunculus rhom- 

 boideus. Anemone ludoviciana, Hackelia americana and others. Much 

 of the terrain is maturely dissected, and consists of steep, forested 

 slopes. The tops of the plateaus are treeless or only sparsely forested. 

 Along the cliffs of the larger streanis there are several northern species 



