﻿MOSSES, 
  LIVERWORTS, 
  AND 
  FERNS 
  

  

  267 
  

  

  252. 
  The 
  nutrition 
  of 
  mosses. 
  The 
  stem-and-leaf 
  arrange- 
  

   ment 
  of 
  the 
  mosses 
  exposes 
  chlorophyll 
  to 
  the 
  light 
  in 
  a 
  differ- 
  

   ent 
  way 
  from 
  that 
  which 
  was 
  found 
  in 
  the 
  algse. 
  With 
  the 
  

   leaves 
  arranged 
  radially 
  about 
  the 
  stem 
  

  

  much 
  more 
  chlorophyll 
  is 
  exposed 
  than 
  

   could 
  be 
  exposed 
  in 
  the 
  same 
  space 
  by 
  

   a 
  prostrate 
  plant. 
  The 
  importance 
  of 
  

   the 
  stem 
  in 
  holding 
  these 
  leaves 
  up 
  

   into 
  the 
  air, 
  thus 
  making 
  the 
  radial 
  

   arrangement 
  possible, 
  is 
  great. 
  The 
  

   expanded 
  portions 
  of 
  the 
  leaves 
  are 
  a 
  

   single 
  layer 
  of 
  cells 
  in 
  thickness, 
  while 
  

   the 
  median 
  portion 
  may 
  consist 
  of 
  

   several 
  layers. 
  Moss 
  plants 
  are 
  often 
  

   favorably 
  placed 
  for 
  securing 
  mois- 
  

   ture 
  when 
  moisture 
  is 
  abundant. 
  The 
  

   whole 
  dense 
  growth 
  made 
  by 
  the 
  

   hundreds 
  of 
  plants 
  that 
  grow 
  together 
  

   may 
  act 
  as 
  a 
  sponge 
  in 
  absorbing 
  and 
  

   holding 
  water, 
  so 
  that 
  at 
  times, 
  when 
  

   one 
  is 
  walking 
  through 
  mosses, 
  water 
  

   runs 
  in 
  streams 
  from 
  those 
  upon 
  

   which 
  he 
  steps. 
  Certain 
  mosses 
  live 
  

   part 
  or 
  all 
  of 
  the 
  time 
  directly 
  in 
  the 
  

   water. 
  On 
  the 
  other 
  hand, 
  when 
  long 
  

   exposed 
  to 
  drying 
  influences, 
  some 
  

   mosses 
  become 
  so 
  dry 
  that 
  they 
  readily 
  

   crumble 
  ; 
  but 
  if 
  not 
  disturbed, 
  they 
  

   proceed 
  to 
  grow 
  whenever 
  there 
  is 
  a 
  

   return 
  of 
  adequate 
  moisture. 
  Mosses 
  

   may 
  also 
  withstand 
  great 
  extremes 
  

   of 
  heat 
  and 
  cold. 
  

  

  253. 
  Peat-bog 
  moss. 
  There 
  are 
  many 
  different 
  kinds 
  of 
  

   mosses, 
  and 
  they 
  are 
  found 
  in 
  almost 
  all 
  kinds 
  of 
  places 
  where 
  

   any 
  plants 
  grow. 
  Peat-bog 
  moss 
  (Spliagnuni) 
  (fig. 
  205) 
  is 
  a 
  

   very 
  striking 
  form 
  which, 
  with 
  other 
  plants, 
  often 
  forms 
  peat. 
  

  

  FIG. 
  205. 
  A 
  peat-bog 
  moss 
  

   (Sphagnum) 
  

  

  About 
  natural 
  size 
  

  

  