﻿CHAPTER 
  XVIII 
  

   THE 
  SEED 
  PLANTS 
  i 
  

  

  266. 
  Introductory. 
  In 
  the 
  earlier 
  chapters 
  of 
  this 
  book 
  we 
  

   dealt 
  only 
  with 
  flowering 
  or 
  seed 
  plants, 
  which 
  belong 
  to 
  the 
  

   fourth 
  great 
  division 
  of 
  the 
  plant 
  kingdom. 
  This 
  division 
  is 
  

   known 
  as 
  the 
  spermatophytes, 
  which 
  means 
  " 
  seed 
  plants." 
  

   In 
  fact, 
  our 
  earlier 
  discussions 
  considered 
  practically 
  no 
  plants 
  

   except 
  members 
  of 
  the 
  second 
  of 
  the 
  two 
  groups 
  of 
  seed 
  

   plants 
  - 
  - 
  the 
  angiosperms, 
  or 
  plants 
  with 
  inclosed 
  seeds. 
  The 
  

   other 
  group 
  of 
  seed 
  plants 
  is 
  the 
  gymnosperms, 
  or 
  plants 
  with 
  

   exposed 
  seeds. 
  Seed 
  plants 
  are 
  the 
  most 
  conspicuous 
  plants 
  

   of 
  the 
  earth, 
  and 
  are 
  the 
  ones 
  which 
  people 
  ordinarily 
  regard 
  

   as 
  composing 
  the 
  plant 
  kingdom. 
  They 
  are 
  most 
  important 
  

   in 
  agriculture, 
  horticulture, 
  landscape 
  and 
  vegetable 
  garden- 
  

   ing, 
  forestry, 
  and 
  the 
  industries. 
  We 
  shall 
  first 
  consider 
  the 
  

   gymnosperms, 
  of 
  which 
  there 
  are 
  over 
  four 
  hundred 
  species, 
  

   some 
  widely 
  distributed 
  and 
  some 
  limited 
  to 
  small 
  areas. 
  

  

  267. 
  Gymnosperms-- 
  the 
  pine 
  as 
  a 
  type. 
  The 
  pine 
  is 
  the 
  

   best 
  general 
  illustration 
  of 
  the 
  gymnosperms 
  and 
  is 
  by 
  far 
  

   the 
  most 
  widely 
  distributed 
  member 
  of 
  the 
  group. 
  Sometimes 
  

   pines 
  form 
  dense 
  forests 
  of 
  tall, 
  straight 
  trees 
  standing 
  close 
  

   together. 
  It 
  is 
  only 
  when 
  thus 
  crowded 
  that 
  they 
  grow 
  tall, 
  

   since, 
  when 
  growing 
  alone 
  in 
  open 
  territory, 
  they 
  secure 
  ample 
  

   light 
  without 
  attain 
  in-' 
  sndi 
  a 
  height. 
  

  

  With 
  a 
  deep-growing 
  central 
  taproot 
  and 
  extensively 
  

   branched 
  lateral 
  roots 
  the 
  pine 
  plant 
  holds 
  its 
  place 
  in 
  the 
  

  

  1 
  This 
  chapter 
  summarizes 
  some 
  of 
  the 
  things 
  said 
  about 
  seed 
  plants 
  in 
  

   the 
  first 
  chapters 
  of 
  this 
  book, 
  and 
  adds 
  discussions 
  whieh 
  will 
  enable 
  the 
  

   student 
  to 
  see 
  in 
  an 
  elementary 
  way 
  the 
  relation 
  of 
  the 
  seed 
  plants 
  to 
  the 
  

   groups 
  of 
  lower 
  plants 
  discussed 
  in 
  the 
  immediately 
  preceding 
  chapters. 
  

  

  282 
  

  

  