﻿334 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  Any 
  very 
  prevalent 
  and 
  troublesome 
  weed 
  will 
  usually 
  be 
  

   found 
  to 
  possess 
  a 
  considerable 
  number 
  of 
  the 
  qualities 
  just 
  

   stated. 
  A 
  good 
  example 
  of 
  this 
  is 
  found 
  in 
  the 
  common 
  sorrel 
  

   (fig. 
  241). 
  It 
  is 
  rapidly 
  propagated 
  by 
  its 
  creeping 
  roots, 
  which 
  

   may 
  form 
  a 
  network 
  throughout 
  a 
  pieee 
  of 
  ground 
  nine 
  feet 
  in 
  

   diameter. 
  As 
  these 
  roots 
  form 
  buds 
  at 
  short 
  intervals, 
  a 
  single 
  

   plant, 
  when 
  let 
  alone, 
  will 
  soon 
  become 
  the 
  center 
  of 
  a 
  colony. 
  

   Sorrel 
  also 
  seeds 
  abundantly, 
  and 
  its 
  seeds 
  

   occur 
  mixed 
  with 
  commercial 
  grass 
  seed 
  and 
  

   clover 
  seed. 
  It 
  is 
  little 
  affected 
  by 
  drought 
  or 
  

   frost 
  and 
  nourishes 
  in 
  poor, 
  thin 
  soils, 
  so 
  that 
  

   neglected 
  pastures 
  often 
  become 
  overrun 
  with 
  

   it. 
  This 
  sorrel, 
  then, 
  is 
  a 
  good 
  example 
  of 
  the 
  

   kind 
  of 
  weed 
  that 
  finds 
  its 
  way 
  where 
  the 
  con- 
  

   ditions 
  are 
  not 
  very 
  fav- 
  

   orable 
  to 
  the 
  growth 
  of 
  

   more 
  robust 
  plants, 
  and 
  

   that 
  makes 
  considerable 
  

   headway 
  beneath 
  the 
  shade 
  

   of 
  crops 
  taller 
  than 
  itself. 
  

  

  An 
  example 
  of 
  the 
  oppo- 
  

   site 
  type 
  of 
  weed, 
  that 
  can- 
  

   not 
  reach 
  any 
  thing 
  like 
  its 
  

   full 
  size 
  except 
  in 
  deep, 
  

   rich 
  ground, 
  is 
  the 
  common 
  

   ragweed 
  (fig. 
  242). 
  Under 
  

   favorable 
  conditions 
  this 
  

   grows 
  so 
  large 
  as 
  to 
  crowd 
  out 
  other 
  plants. 
  It 
  cannot 
  repro- 
  

   duce 
  itself 
  except 
  by 
  seed, 
  but 
  the 
  seeds 
  are 
  abundant 
  (often 
  

   more 
  than 
  20,000 
  in 
  number) 
  ; 
  the 
  seedlings 
  soon 
  become 
  

   stout 
  and 
  branching, 
  with 
  a 
  deep 
  taproot 
  which 
  robs 
  all 
  

   neighl 
  ii 
  >i 
  i 
  i 
  ig 
  plants 
  of 
  water 
  and 
  food 
  materials. 
  Other 
  familial- 
  

   weeds 
  of 
  rich 
  ground 
  with 
  the 
  robust 
  habit 
  of 
  the 
  ragweed 
  are 
  

   pigweeds 
  ( 
  Chenopodiuni) 
  of 
  several 
  species, 
  two 
  or 
  three 
  species 
  

   of 
  rough 
  pigweeds 
  (^Amaranihw), 
  several 
  kinds 
  of 
  dock, 
  the 
  

   Indian 
  mallow 
  or 
  butter 
  print 
  (Abutilori), 
  and 
  sunflowers. 
  

  

  FIG. 
  'J41. 
  Portion 
  of 
  a 
  plant 
  of 
  the 
  

   common 
  sorrel 
  

  

  The 
  leaf 
  is 
  drawn 
  about 
  one 
  half 
  natural 
  

  

  si/i'. 
  Tin- 
  niiiniii.u 
  roots 
  of 
  a 
  lar^r 
  specimen 
  

  

  would 
  he 
  at 
  least 
  sixty 
  times 
  as 
  lout; 
  as 
  the 
  

  

  pieee 
  here 
  shown 
  

  

  