﻿CHAPTER 
  XIII 
  

   HOW 
  PLANTS 
  ARE 
  CLASSIFIED 
  

  

  181. 
  Introductory. 
  In 
  preceding 
  discussions 
  we 
  have 
  often 
  

   had 
  occasion 
  to 
  speak 
  of 
  closely 
  related 
  plants 
  which, 
  while 
  

   different 
  in 
  some 
  ways, 
  were 
  sufficiently 
  similar 
  to 
  enable 
  us 
  

   to 
  recognize 
  their 
  likeness. 
  Thus 
  we 
  speak 
  of 
  different 
  kinds 
  

   of 
  grasses, 
  different 
  kinds 
  of 
  corn, 
  or 
  different 
  kinds 
  of 
  oaks. 
  

   Also, 
  in 
  actual 
  practice 
  many 
  other 
  bases 
  of 
  grouping 
  are 
  

   used, 
  as 
  is 
  suggested 
  when 
  we 
  speak 
  of 
  agricultural 
  plants, 
  

   tropical 
  plants, 
  desert 
  plants, 
  water 
  plants, 
  and 
  poisonous 
  

   plants. 
  Similarity 
  in 
  structure 
  offers 
  a 
  basis 
  of 
  classification 
  

   that 
  is 
  commonly 
  used. 
  By 
  means 
  of 
  this 
  basis 
  plants 
  that 
  

   resemble 
  each 
  other 
  most 
  closely 
  are 
  grouped 
  together 
  ; 
  then 
  

   the 
  groups 
  having 
  the 
  closest 
  resemblance 
  are 
  combined 
  into 
  

   a 
  larger 
  group, 
  until 
  finally 
  all 
  the 
  larger 
  groups 
  compose 
  the 
  

   last 
  and 
  largest 
  group 
  --the 
  plant 
  kingdom. 
  

  

  182. 
  Oaks 
  as 
  illustrations. 
  A 
  good 
  illustration 
  of 
  the 
  

   smaller 
  groupings 
  of 
  plants 
  may 
  be 
  had 
  by 
  referring 
  to 
  some 
  

   of 
  the 
  common 
  oaks. 
  In 
  various 
  parts 
  of 
  the 
  United 
  States 
  

   we 
  find 
  the 
  white 
  oak, 
  bur 
  oak, 
  red 
  oak, 
  black 
  oak, 
  blackjack 
  

   oak, 
  live 
  oak, 
  and 
  many 
  others. 
  There 
  are 
  certain 
  special 
  or 
  

   specific 
  differences 
  between 
  these 
  oaks, 
  as 
  is 
  shown 
  by 
  their 
  

   acorns 
  and 
  leaves 
  (fig. 
  164), 
  and 
  each 
  specific 
  kind 
  of 
  oak 
  

   is 
  called 
  a 
  species 
  and 
  has 
  a 
  species 
  name, 
  as 
  alba 
  (white), 
  

   rnlra 
  (red), 
  macrocarpa 
  l 
  (bur), 
  etc. 
  Furthermore, 
  these 
  and 
  

   all 
  the 
  other 
  species 
  which 
  we 
  call 
  the 
  oaks 
  are 
  grouped 
  to- 
  

   gether 
  into 
  one 
  genus 
  (or 
  kind), 
  the 
  genus 
  name 
  of 
  the 
  oaks 
  

   being 
  Quercus. 
  Therefore 
  a 
  genus 
  consists 
  of 
  the 
  different 
  

  

  1 
  The 
  original 
  meaning 
  of 
  macrocarpa 
  is 
  "large-fruited," 
  or 
  "large- 
  

   seeded." 
  

  

  194 
  

  

  