156 BOTANICAL GAZETTE [MARCH 
the Chicago prairies will ever become forested is a question not 
easily answered. There are signs of it in some places, as at 
Stony island, but this topic needs more detailed treatment than 
can be given here. 
The processes outlined in this section are rapid. The meso- 
phytic prairie or forest develops from the lake or marsh, while 
the region as a whole still retains a young topography. Thus 


Fic. 25.— Prairie at Pullman in which the compass plant (Silphium) grows with 
the grasses. This prairie is much older and drier than that shown in fg. 24. 
this mesophytic assemblage, like that of the ravine slope, is 
bound to pass away, though its life tenure is much longer. 
Sooner or later river action will enter; there will be developed 
ravines, xerophytic bluffs, and ultimately flood plains, again 
with a mesophytic flora. A broad survey then shows a rapid 
development to a somewhat prolonged temporary climax, and 
finally after ravine and bluff vicissitudes there appears the true 
and more enduring climax of the mesophytic flood plain. 
¥ 3. THE UPLAND SERIES. 
A. The rock hill—While all of a land area is eventually 
worked over by stream activities and can thus be referred to the 
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