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  INTRODUCTION 
  TO 
  BOTANY 
  

  

  species 
  that 
  belong 
  to 
  it. 
  A 
  careful 
  study 
  of 
  figure 
  164 
  will 
  

   give 
  some 
  notion 
  of 
  the 
  relative 
  resemblances 
  of 
  two 
  struc- 
  

   tures 
  in 
  these 
  six 
  species 
  of 
  Quercus. 
  In 
  speaking 
  of 
  plants 
  it 
  

   is 
  customary 
  to 
  use 
  both 
  genus 
  and 
  species 
  name 
  (that 
  is, 
  the 
  

   binomial 
  system 
  of 
  names), 
  as 
  Quercus 
  alba; 
  or, 
  more 
  often, 
  

   we 
  use 
  the 
  common 
  name, 
  as 
  ivhite 
  oak. 
  Elementary 
  botany 
  

   formerly 
  concerned 
  itself 
  chiefly 
  with 
  attempts 
  to 
  learn 
  the 
  

   genus 
  and 
  species 
  names 
  and 
  the 
  proper 
  classification 
  of 
  seed 
  

   plants. 
  We 
  are 
  now 
  concerned 
  more 
  with 
  how 
  plants 
  live 
  than 
  

   with 
  what 
  their 
  botanical 
  names 
  are. 
  

  

  183. 
  The 
  leading 
  groups 
  of 
  plants. 
  Those 
  genera 
  (plural 
  

   of 
  genus) 
  which 
  resemble 
  one 
  another 
  are 
  grouped 
  together 
  

   into 
  a 
  family 
  ; 
  families 
  with 
  sufficiently 
  close 
  resemblances 
  

   are 
  grouped 
  into 
  an 
  order 
  ; 
  orders 
  are 
  grouped 
  into 
  classes; 
  

   and 
  classes 
  into 
  great 
  groups. 
  A 
  study 
  of 
  the 
  following 
  divi- 
  

   sions 
  of 
  the 
  plant 
  kingdom 
  will 
  enable 
  you 
  to 
  see 
  the 
  relations 
  

   that 
  these 
  divisions 
  bear 
  to 
  one 
  another, 
  and 
  the 
  relations 
  of 
  

   genus 
  and 
  species 
  names 
  to 
  the 
  whole 
  plan 
  of 
  classification. 
  

  

  Plant 
  kingdom 
  

   Great 
  groups 
  

   Classes 
  

  

  (Sometimes 
  sub-classes) 
  

   Orders 
  

   Families 
  

   Genera 
  

   Species 
  

  

  (Sometimes 
  varieties) 
  

  

  The 
  four 
  great 
  groups 
  of 
  plants 
  are 
  

  

  "V* 
  Spermatophytes, 
  the 
  seed 
  plants 
  in 
  which 
  are 
  : 
  

  

  Angiosperms, 
  or 
  plants 
  with 
  inclosed 
  seeds; 
  

   Gymnosperms, 
  or 
  plants 
  with 
  exposed 
  seeds. 
  

   Pteridophytes, 
  the 
  fern 
  plants, 
  including 
  the 
  common 
  ferns 
  and 
  other 
  

  

  fern-like 
  plants 
  that 
  are 
  not 
  so 
  common. 
  

   /- 
  Bryophytes, 
  including 
  liverworts 
  and 
  mosses. 
  

  

  . 
  Thallophytes, 
  including 
  the 
  lowest 
  and 
  simplest 
  plants 
  the 
  fission 
  

   plants, 
  the 
  algae, 
  and 
  the 
  fungi. 
  

  

  Some 
  of 
  these 
  groups 
  will 
  be 
  very 
  briefly 
  considered 
  in 
  the 
  

   chapters 
  immediately 
  following. 
  

  

  