﻿PREFACE 
  v 
  

  

  Valuable 
  suggestions 
  from 
  many 
  teachers 
  and 
  students 
  of 
  

   botany 
  have 
  been 
  gladly 
  received, 
  and 
  these 
  will 
  doubtless 
  serve 
  

   to 
  render 
  the 
  book 
  more 
  helpful 
  and 
  usable 
  than 
  it 
  otherwise 
  

   would 
  have 
  been. 
  Especial 
  thanks 
  are 
  due 
  to 
  Dr. 
  Norman 
  

   MacLeod 
  Harris 
  of 
  the 
  Department 
  of 
  Bacteriology 
  of 
  The 
  

   University 
  of 
  Chicago, 
  who 
  has 
  read 
  the 
  chapter 
  on 
  bacteria 
  ; 
  

   and 
  to 
  Mr. 
  William 
  L. 
  Eikenberry 
  of 
  the 
  University 
  High 
  

   School, 
  Chicago, 
  who 
  by 
  his 
  frequent 
  suggestions, 
  based 
  

   on 
  extensive 
  experience, 
  has 
  been 
  constantly 
  helpful 
  in 
  the 
  

  

  preparation 
  of 
  this 
  book. 
  

  

  JOSEPH 
  Y. 
  BERGEN 
  

   OTIS 
  W. 
  CALDWELL 
  

  

  