﻿CONTRIBUTIONS 
  TO 
  THE 
  BIOLOGY 
  OF 
  THE 
  GREAT 
  LAKES. 
  

  

  THE 
  BIOLOGICAL 
  RELATION 
  OF 
  AQUATIC 
  PLANTS 
  

   TO 
  THE 
  SUBSTRATUM. 
  

  

  BY 
  

  

  RAYMOND 
  H. 
  POND. 
  

  

  483 
  

  

  