WATER MARGIN COMMUNITIES 183 
II]. GENERAL DISCUSSION 
The areas which we have been discussing in this chapter are the 
tension lines between the land and the water. It is in such areas that 
ecologists have learned most about succession and about the tendencies 
141 
Fic. 140.—Pond 95, showing the death of the pond by the growth of buttonbush. 
Fic. 141.—The shiny salamander (Plethodon glutinosus); about twice natural 
size (after Fowler). 
and processes in animal formations and associations. In this chapter 
we first considered the marshes which border the lakes and ponds about 
Chicago. Dr. Cowles and others have pointed out that lakes and ponds 
are filled by organic débris and that bulrushes invade from the shore and 
“capture” the ponds and lakes. As the bulrushes and other plants 
