Dr.. Cowles' TIiRorv of Cilassif icat ion . 



1. That natijre is dynamic not stactic. 



2. That the presence of plants depends upon the topographical con- 

 ditions of the place, almost entirely. As a region gets older, the 

 topography has more and more to do with the flora, and tlie ceology, 

 less and less. 



3. Topograpiiy depends on dynaraics, not statics. 



4. That plant societies are made w]iat they are largely by past 

 influences, since the vegetation lage behind th.e topocraphy. Res-olt 

 of accumulative effects. 



Tlie vegetation of any district is a complex resultant of past b.m. 



present. Accumulative effect of environment showzi h:" the increase 



of humus. Eacli plant society hy its own existence prepares tlie 



way for its own do?/nfall and its replacement by something else. 



Hence there must he definite suvBcession of plants. A r-enetic 



classification such as this is "based 021 relations. Peat hogs and 



heaths are genetically coniaected. 



Topo^-rauhic Gh^n^eg. 



Two great agencies at work in a region, denudation and deposition. 



3ffect of such processes, since highest hills most eroded and highest 



valleys less filled xip, is planation. A hill necessarily ra-ast be 



xerophirtic and a Valley liydrophytic ; hence as planation increases, 



the ultimate end of all plant soci6ties over inland areas where 



climate is favorable, seems to be to reduce all to mesophytes. 



Criistal movements also have to do witli this classification, 

 Atkinson's 10. ,"574- 42o. Coulter's Plant Relations. 



