﻿204 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  In 
  moist 
  and 
  shady 
  places 
  protonema 
  may 
  grow 
  until 
  great 
  

   mats 
  are 
  formed 
  upon 
  the 
  soil, 
  old 
  logs, 
  etc., 
  and 
  in 
  these 
  

   places 
  the 
  alga-like 
  protonema 
  may 
  live 
  for 
  several 
  years. 
  

  

  At 
  times 
  some 
  of 
  the 
  protonemal 
  cells 
  produce 
  outgrowths 
  

   which 
  divide 
  l>y 
  oblique 
  walls 
  and 
  form 
  buds 
  (fig. 
  203, 
  B 
  ami 
  b). 
  

   The 
  binls 
  may 
  become 
  dormant 
  and 
  lie 
  for 
  months 
  or 
  even 
  

   longer, 
  and 
  then 
  continue 
  to 
  grow 
  ; 
  or 
  there 
  may 
  be 
  no 
  resting 
  

   period. 
  When 
  they 
  grow, 
  the 
  outermost 
  cells 
  produce 
  leaves, 
  

   the 
  central 
  ones 
  become 
  the 
  stem, 
  and 
  from 
  the 
  lower 
  ones 
  the, 
  

   root-like 
  hairs 
  (rhizoids) 
  grow. 
  The 
  rhizoids 
  descend 
  into 
  the 
  

   soil 
  or 
  other 
  substance 
  below 
  the 
  plant, 
  and 
  the 
  leaves 
  and 
  

   stem 
  rise 
  into 
  the 
  air. 
  The 
  buds, 
  therefore, 
  which 
  grow 
  from 
  

   the 
  protonema 
  are 
  the 
  beginnings 
  of 
  the 
  leafy 
  moss 
  plant. 
  

  

  250. 
  Sexual 
  and 
  asexual 
  reproduction 
  in 
  the 
  moss. 
  At 
  the 
  

   tip 
  of 
  the 
  stem 
  of 
  the 
  leafy 
  plant, 
  more 
  or 
  less 
  inclosed 
  by 
  

   the 
  leaves, 
  the 
  sex 
  organs 
  of 
  the 
  moss 
  develop. 
  These 
  are 
  of 
  

   two 
  kinds, 
  and 
  with 
  them 
  there 
  are 
  usually 
  taller 
  sterile 
  fila- 
  

   ments, 
  which 
  bear 
  chlorophyll 
  and 
  may 
  serve 
  to 
  protect 
  the 
  

   sex 
  organs. 
  In 
  some 
  kinds 
  of 
  mosses 
  only 
  one 
  kind 
  of 
  sex 
  

   organ 
  is 
  borne 
  on 
  a 
  single 
  plant, 
  while 
  in 
  other 
  kinds 
  both 
  

   are 
  produced 
  on 
  the 
  same 
  plant 
  at 
  the 
  same 
  time. 
  Neither 
  

   can 
  be 
  studied 
  without 
  magnification, 
  although 
  the 
  male 
  sex 
  

   organs 
  may 
  sometimes 
  be 
  detected 
  without 
  a 
  lens. 
  

  

  The 
  <treli(>nn>ihun, 
  the 
  female 
  sex 
  organ, 
  is 
  similar 
  in 
  func- 
  

   tion 
  to 
  the 
  oogonium 
  in 
  I'mif/tcrin. 
  It 
  is 
  flask-like 
  and 
  has 
  

   an 
  elongated 
  neck 
  (fig. 
  204, 
  Z>). 
  In 
  the 
  swollen 
  part 
  of 
  the 
  

   archegoninm 
  the 
  egg 
  is 
  formed. 
  When 
  the 
  egg 
  is 
  mature, 
  the 
  

   central 
  cells 
  of 
  the 
  neck 
  become 
  gelatinous, 
  and 
  the 
  end 
  of 
  

   the 
  neck 
  opens 
  so 
  that 
  there 
  is 
  a 
  passageway 
  through 
  the 
  neck 
  

   down 
  to 
  the 
  egg. 
  The 
  male 
  sex 
  organ, 
  the 
  <int/ifri</iinn, 
  is 
  

   club-shaped 
  ( 
  lig. 
  204,.!), 
  being 
  attached 
  by 
  its 
  smaller 
  end 
  

   to 
  the 
  tip 
  of 
  the 
  plant 
  stem. 
  When 
  the 
  antheridium 
  opens, 
  

   its 
  thousands 
  of 
  sperms 
  are 
  set 
  free. 
  The 
  sperms 
  swim 
  with 
  

   great 
  activity, 
  and 
  some 
  of 
  them 
  may 
  come 
  into 
  the 
  vicinity 
  

   of 
  the 
  neck 
  of 
  the 
  archegonium. 
  One 
  or 
  more 
  make 
  their 
  way 
  

   down 
  through 
  the 
  gelatinous 
  neck 
  of 
  the 
  archegonium 
  to 
  the 
  

  

  

  