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  INTRODUCTION 
  TO 
  BOTANY 
  

  

  that 
  seed 
  plants 
  were 
  also 
  present 
  during 
  that 
  time. 
  It 
  was 
  

   later, 
  during 
  the 
  next 
  age, 
  that 
  gymnosperms 
  became 
  most 
  

   abundant. 
  There 
  are 
  fossil 
  remains 
  of 
  giant 
  gymnosperms 
  - 
  

   trees 
  so 
  well 
  preserved 
  that 
  even 
  the 
  nature 
  of 
  the 
  seeds 
  may 
  

   be 
  determined. 
  In 
  those 
  times 
  gymnosperms 
  were 
  everywhere. 
  

   The 
  "big 
  trees" 
  and 
  redwoods 
  extended 
  to 
  Greenland, 
  and 
  

   other 
  groups 
  now 
  well-nigh 
  extinct 
  grew 
  in 
  profusion 
  over 
  

   very 
  wide 
  areas. 
  Pines 
  did 
  not 
  become 
  abundant 
  until 
  late 
  

   in 
  the 
  development 
  of 
  gymnosperms, 
  and 
  they 
  are 
  still 
  widely 
  

   distributed 
  and 
  fairly 
  luxuriant 
  in 
  their 
  growth. 
  Xo 
  doubt 
  

   the 
  climate 
  and 
  physical 
  conditions 
  upon 
  the 
  earth 
  have 
  

   undergone 
  very 
  extensive 
  changes 
  during 
  the 
  earth's 
  history, 
  

   and 
  in 
  consequence 
  plant 
  life 
  has 
  changed. 
  Therefore 
  the 
  

   plants 
  now 
  surviving 
  from 
  former 
  abundant 
  groups 
  have 
  prob- 
  

   ably 
  undergone 
  many 
  alterations 
  since 
  the 
  times 
  when 
  their 
  

   ancestors 
  were 
  dominant. 
  But 
  they 
  stand 
  as 
  living 
  evidences 
  

   of 
  the 
  kinds 
  of 
  plants 
  that 
  were 
  most 
  abundant 
  before 
  the 
  last 
  

   great 
  group 
  became 
  the 
  dominant 
  plants 
  of 
  the 
  earth. 
  That 
  

   group 
  is 
  the 
  angiosperms. 
  

  

  281. 
  Angiosperms: 
  their 
  diversity. 
  This 
  is 
  the 
  second 
  

   group 
  of 
  the 
  seed 
  plants 
  and 
  is 
  therefore 
  the 
  highest 
  group 
  

   of 
  the 
  plant 
  kingdom. 
  Angiosperms 
  exhibit 
  the 
  widest 
  varia- 
  

   tion 
  in 
  form 
  and 
  in 
  habits 
  of 
  living. 
  As 
  water 
  plants 
  they 
  

   may 
  be 
  submerged 
  or 
  free-floating, 
  or 
  may 
  grow 
  in 
  water 
  part 
  

   of 
  the 
  time 
  and 
  on 
  land 
  part 
  of 
  the 
  time; 
  they 
  may 
  grow 
  in 
  

   nylons 
  that 
  are 
  so 
  dry 
  and 
  exposed 
  as 
  to 
  make 
  life 
  seem 
  

   impossible. 
  They 
  thrive 
  luxuriantly 
  in 
  the 
  tropics, 
  and 
  even 
  

   live 
  upon 
  the 
  ice 
  in 
  frigid 
  regions. 
  They 
  may 
  live 
  as 
  epiphytes, 
  

   or 
  as 
  vines 
  climbing 
  upon 
  other 
  plants. 
  They 
  may 
  be 
  parasites, 
  

   saprophytes, 
  or 
  even 
  carnivorous 
  plants. 
  In 
  form 
  the 
  angio- 
  

   sperms 
  range 
  from 
  diminutive 
  floating 
  disks 
  to 
  gigantic 
  trees. 
  

   In 
  length 
  of 
  life 
  they 
  range 
  from 
  those 
  that 
  complete 
  their 
  life 
  

   round 
  many 
  times 
  during 
  one 
  year 
  to 
  individual 
  plants 
  that 
  

   live 
  to 
  be 
  several 
  centuries 
  old. 
  

  

  The 
  total 
  number 
  of 
  species 
  of 
  angiosperms 
  is 
  not 
  definitely 
  

   kno\vn, 
  but 
  botanists 
  agree 
  that 
  there 
  are 
  over 
  one 
  hundred 
  

  

  