﻿THE 
  SEED 
  PLANTS 
  

  

  289 
  

  

  tissue 
  in 
  the 
  ferns, 
  but 
  in 
  the 
  pines 
  and 
  then- 
  relatives 
  the 
  

  

  vascular 
  tissue 
  is 
  organized 
  into 
  a 
  stem 
  that 
  may 
  attain 
  great 
  

  

  height 
  and 
  thickness 
  (fig. 
  222). 
  These 
  plants 
  have 
  been 
  

  

  highly 
  successful 
  in 
  the 
  struggle 
  for 
  

  

  light. 
  Such 
  plants 
  also 
  have 
  quite 
  

  

  extensive 
  woody 
  root 
  systems, 
  which 
  

  

  serve 
  to 
  anchor 
  these 
  great 
  trees 
  and 
  

  

  to 
  gather 
  the 
  water 
  and 
  substances 
  

  

  in 
  solution 
  that 
  are 
  conducted 
  through 
  

  

  the 
  whole 
  length 
  of 
  the 
  stem 
  to 
  the 
  

  

  leaves. 
  

  

  The 
  significance 
  of 
  the 
  stems 
  of 
  

   gymnosperms 
  and 
  some 
  angiosperms 
  

   to 
  those 
  industries 
  that 
  use 
  timber 
  

   is 
  difficult 
  to 
  estimate. 
  Timber 
  is 
  

   used 
  for 
  all 
  sorts 
  of 
  useful 
  and 
  orna- 
  

   mental 
  products, 
  and 
  many 
  kinds 
  of 
  

   industry 
  are 
  dependent 
  upon 
  timber 
  ; 
  

   but 
  it 
  must 
  be 
  remembered 
  that 
  

   woody 
  stems 
  are 
  developed 
  as 
  struc- 
  

   tures 
  which 
  support 
  leaves 
  and 
  con- 
  

   duct 
  food 
  materials 
  to 
  and 
  from 
  them, 
  

   in 
  connection 
  with 
  the 
  plants' 
  strug- 
  

   gle 
  to 
  live, 
  and 
  that 
  man's 
  use 
  of 
  

   this 
  timber 
  is, 
  botanically, 
  merely 
  

   incidental. 
  

  

  274. 
  Pine 
  cones. 
  Two 
  kinds 
  of 
  

   cones 
  are 
  borne 
  upon 
  pines 
  : 
  one 
  is 
  

   the 
  seed-forming 
  cone 
  (fig. 
  223) 
  ; 
  the 
  

   other 
  is 
  the 
  staminate 
  cone. 
  The 
  

   seed 
  cone 
  is 
  composed 
  of 
  heavy, 
  leaf- 
  

   like 
  parts, 
  on 
  the 
  upper 
  sides 
  of 
  

   which 
  the 
  developing 
  seeds 
  or 
  ovules 
  

   are 
  formed. 
  Within 
  the 
  ovule 
  the 
  egg 
  is 
  produced 
  (fig. 
  224). 
  

   The 
  staminate 
  cones 
  appear 
  early 
  in 
  the 
  spring, 
  shed 
  their 
  

   pollen, 
  and 
  soon 
  wither 
  and 
  fall 
  to 
  the 
  ground. 
  These 
  cones 
  

  

  FIG. 
  224. 
  Diagram 
  of 
  part 
  of 
  

  

  a 
  seed 
  cone 
  of 
  a 
  pine, 
  with 
  

  

  ovules 
  in 
  normal 
  position 
  

  

  S, 
  sporophylls, 
  or 
  leaf-like 
  parts 
  

   of 
  the 
  cone; 
  O, 
  ovule; 
  /, 
  the 
  

   covering 
  of 
  the 
  ovule, 
  called 
  

   the 
  integument 
  ; 
  FG, 
  the 
  female 
  

   gametophyte, 
  which 
  hears 
  the 
  

   archegonium 
  A, 
  in 
  which 
  the 
  

   egg 
  is 
  formed 
  ; 
  Pt, 
  pollen 
  tubes 
  

   from 
  pollen 
  grains 
  which 
  lie 
  

   upon 
  the 
  tip 
  of 
  the 
  ovule 
  

  

  