32 ILLINOIS ACADEMY OF SCIENCE 
sand, and swamps, to the well-drained soil of the upland 
prairies. 
2. The development of the physiography of these pioneer 
habitats is followed by dynamic successions of the plant asso- 
ciations. The associations in these successions differ in each 
particular case according to the initial habitat, but in all cases 
they ultimately lead to this climax prairie. 
3. Andropogon furcatus is the most abundant grass of this 
climax prairie, and usually occupies more than 80 per cent of 
the total area of the association which it represents. This fact 
suggests that Andropogon furcatus is the climax grass of the 
Illinois prairies. 
4. In their order from pioneer to climax, the most impor- 
tant associations of the hydrarch successions are Scirpus fluvi- 
atilis, Carex vesicaria, Spartina Michauxiana, Calamagrostis 
canadensis, Panicum virgatum, and Andropogon furcatus. The 
most important associations of the xerarch succession on sand 
are Panicum pseudopubescens, Andropogon scoparius, and An- 
dropogon furcatus. 
5. During long-continued grazing, the Andropogon and 
Panicum virgatum associations are displaced by a sod of blue- 
grass (Poa pratensis). Each of the other associations is like- 
wise displaced by more or less definite types of pasture plants. 
6. Owing to the numerous diverse types of disturbance by 
man, the associations of prairie plants on railroad right-of- 
ways are unnatural, and in certain respects do not agree with 
those found in undisturbed virgin areas. 
Relic patches of these virgin associations on these right-of- 
ways are, however, still abundant enough to give a general pic- 
ture of the original prairies. Data collected from this point of 
view show that most of the prairie area of old glacial regions 
of the State had reached the Andropogon furcatus stage before 
the coming of the plowman, while much of the prairie area of 
the Wisconsin glaciation was dominated by Spartina Michauzt- 
ana, Calamagrostis canadensis, or Panicum virgatum, accord- 
ing to the development of the drainage conditions. This con- 
clusion is further substantiated by the word of the older inhab- 
itants who saw these prairies in all their original grandeur. 
