Foreword 



ated together. These groups are made up of plants that have 

 adapted themselves to the same environmental conditions, 

 producing what is called a "plant association." This associa- 

 tion of plants is determined to a great extent by the influence 

 of the environment. Only those plants that can propagate 

 naturally in dry open places will be found upon dry exposed 

 hillsides. Plants requiring a great deal of moisture will be 

 found only in shady ravines. Once the plants have become 

 established, however, their very establishment creates a change 

 in environmental conditions. Thus they pave the way for an 

 association of plants requiring other conditions than they 

 themselves required, — other conditions of soil, atmosphere, 

 moisture and shade. These new conditions tend to eliminate 

 the plants first occupying the area. 



In other words one association of plants will occupy an 

 area only so long as the environment is favorable to its devel- 

 opment. Each association will be followed by an association 

 of a different type. This series of associations produces what 

 is called a "plant succession." Thus in the ecology of plants 

 there is found this dynamic phenomenon in which no associa- 

 tion is static, and plant associations merge one into another 

 in a succession. 



To determine the plant associations in any area, as for 

 example, Dutchess County, one must select the outstanding 

 types as unit association's, and study the content of these 

 types in detail. The associations in Dutchess County group 

 themselves into an Upland Succession and Lowland Succes- 

 sions. The latter are subdivided into the successions found in 

 Lakes and Ponds, Bogs, Rivers and Streams, and Ravines. 



The following are the associations of plants found in the 

 Upland Succession. 



