Gleason : Unsolved problems of the prairies 



271 



For lack of a better name this type of succession may be called 

 abnormal, to distinguish it from the normal type mentioned before.* 

 The abnormal succession here is between Upper Austral prairies 

 and Upper Austral forest. The prairie came in contact also with 

 the transition zone forests at the north, and between them there is 

 still another type of succession to be studied, even more abnormal 

 in nature, and possibly entirely different in operation. Our Illi- 

 nois prairies also approached the Lower Austral zone in southern 



4 



Illinois, but there was apparently no transition between them. 



These questions are by no means the only ones still awaiting 

 investigation in the Illinois prairies. Others equally important 

 will present themselves at once to every ecologist Local condi- 

 tions will produce local questions whose solution may throw much 

 light on the broader problems of the prairies as a whole. Those 

 that I have given refer entirely to the phytogeographical and as- 

 sociational sides of ecology. I have not touched upon any of the 

 numerous and varied questions of individual or physiological 

 ecology, such as light relation, water requirements, transpiration, 

 individual or specific relations to the environment, and the like ; 

 nor have I mentioned any questions concerning the taxonomic 

 side of the flora, which should still yield many interesting species 

 to the modern systematist. 



University of Illinois, 

 Urbana, Illinois. 



* An excellent discussion of these two general types of succession has been given 

 by Transeau in his ** The bogs and bog flora of the Huron River valley,'* Bot, Gaz. 

 40: 351-375, 418-448, 1905 ; 41 : 17-42./ 1-16, 1906. See especially 41 : 38. 



