﻿170 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  Competition 
  sometimes 
  results 
  in 
  killing 
  outright 
  most 
  of 
  

   the 
  competing 
  plants; 
  sometimes 
  it 
  only 
  renders 
  them 
  dwarf- 
  

   ish 
  and 
  incapable 
  of 
  producing 
  many 
  llowers 
  or 
  seeds. 
  

  

  The 
  means 
  In 
  which 
  the 
  successful 
  individuals 
  weaken 
  or 
  

   kill 
  their 
  neighbors 
  art' 
  mainly 
  

  

  1. 
  Overshadowing, 
  resulting 
  in 
  deficient 
  photosynthesis 
  in 
  

   the 
  shaded 
  plants 
  from 
  lack 
  of 
  light. 
  

  

  2. 
  Robbing 
  the 
  defeated 
  plants 
  of 
  water. 
  

  

  3. 
  Robbing 
  them 
  of 
  soluble 
  salts, 
  such 
  as 
  nitrates 
  and 
  phos- 
  

  

  phates 
  of 
  the 
  soil. 
  

  

  The 
  deprivation 
  

   of 
  sufficient 
  water 
  

   and 
  salts 
  interferes 
  

   with 
  the 
  nutrition 
  

   of 
  the 
  overcrowded 
  

   plants 
  and 
  may 
  soon 
  

   stop 
  their 
  growth. 
  

  

  162. 
  Mechanisms 
  

   for 
  distributing 
  seeds. 
  

   Many 
  seeds, 
  such 
  as 
  

   those 
  of 
  the 
  catalpa, 
  

   the 
  milkweed, 
  and 
  

   the 
  willow, 
  have 
  

   wings 
  or 
  tufts 
  of 
  

   down 
  which 
  insure 
  

   their 
  being 
  carried 
  

   considerable 
  distances 
  by 
  the 
  wind. 
  Tufted 
  fruits, 
  such 
  as 
  those 
  

   of 
  the 
  thistle 
  and 
  the 
  dandelion 
  ( 
  lig. 
  147), 
  are 
  familiar 
  to 
  most 
  

   people. 
  Sometimes 
  the 
  plant 
  retains 
  the 
  seeds 
  or 
  fruits 
  for 
  

   months 
  after 
  they 
  are 
  ripened, 
  and 
  thus 
  secures 
  their 
  gradual 
  

   dispersal. 
  The 
  globular 
  clusters 
  of 
  fruits 
  of 
  the 
  sycamore 
  

   (fig. 
  148) 
  remain 
  on 
  the 
  tree 
  during 
  the 
  entire 
  winter 
  many 
  of 
  

   t 
  hem 
  even 
  till 
  the 
  new 
  crop 
  of 
  leaves 
  has 
  appeared 
  in 
  the 
  spring. 
  

   Frequently 
  the 
  pod, 
  or 
  capsule, 
  is 
  so 
  constructed 
  that 
  it 
  

   opens 
  at 
  the 
  top 
  (fig. 
  149) 
  and 
  scatters 
  seeds 
  whenever 
  it 
  is 
  

   swung 
  to 
  and 
  fro 
  by 
  the 
  wind 
  or 
  jostled 
  by 
  a 
  passing 
  animal. 
  

  

  FIG. 
  151. 
  Fruit- 
  <>!' 
  tin- 
  wild 
  black 
  cherry, 
  a 
  very 
  

   valuable 
  timber 
  tree 
  

  

  The 
  srrds, 
  \\hich 
  are 
  h;tnl 
  and 
  indigestible, 
  an- 
  

  

  srminatcd 
  mainly 
  l>y 
  birds. 
  One 
  half 
  natural 
  si/.u 
  

  

  