﻿236 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  usually 
  appears. 
  It 
  grows 
  in 
  and 
  about 
  our 
  homes 
  in 
  great 
  

  

  abundance, 
  upon 
  bread, 
  fruits, 
  and 
  other 
  favorable 
  nutrient 
  sub- 
  

   stances 
  that 
  are 
  left 
  exposed. 
  When 
  young 
  the 
  mold 
  is 
  white, 
  

   only 
  assuming 
  its 
  blackish 
  appearance 
  when 
  spores 
  are 
  formed. 
  

   223. 
  Vegetative 
  structures, 
  and 
  nutrition 
  of 
  bread 
  mold. 
  A 
  

   mass 
  of 
  growing 
  bread 
  mold 
  is 
  composed 
  of 
  many 
  white 
  

   threads 
  grown 
  together 
  until 
  they 
  have 
  become 
  closely 
  inter- 
  

   woven. 
  Each 
  thread 
  is 
  called 
  a 
  7////<7^/ 
  (" 
  a 
  single 
  web"), 
  and 
  

   the 
  whole 
  network 
  of 
  hyplue 
  is 
  the 
  mycelium, 
  or 
  fungus 
  mass. 
  

  

  FIG. 
  184. 
  Bread 
  mold 
  

  

  At 
  the 
  left 
  is 
  a 
  slightly 
  magnitied 
  illustration 
  of 
  plants, 
  one 
  of 
  which 
  has 
  given 
  

   rise 
  to 
  the 
  other 
  by 
  means 
  of 
  a 
  runner, 
  or 
  stolon. 
  1 
  >escendii:g 
  are 
  llie 
  rhizoids 
  and 
  

   ascending 
  are 
  the 
  aerial 
  brandies, 
  upon 
  the 
  tips 
  of 
  which 
  spores 
  are 
  borne 
  within 
  

   sporangia. 
  At 
  the 
  right 
  a 
  more 
  highly 
  niagnitied 
  sporangium 
  is 
  shown. 
  Its 
  wall 
  

   ("') 
  incloses 
  many 
  spores 
  (a), 
  through 
  which 
  may 
  he 
  seen 
  the 
  columella 
  (<), 
  which 
  

   is 
  the 
  swollen 
  tip 
  of 
  the 
  stalk 
  upon 
  which 
  the 
  sporangium 
  is 
  borne. 
  This 
  wall 
  may 
  

   be 
  broken 
  away, 
  so 
  as 
  to 
  leave 
  some 
  of 
  the 
  spores 
  lying 
  upon 
  the 
  cohunella, 
  as 
  is 
  

   seen 
  in 
  two 
  cases 
  of 
  the 
  plants 
  sho\\ 
  n 
  at 
  the 
  left 
  

  

  Careful 
  examination 
  also 
  shows 
  that 
  some 
  of 
  the 
  hyplue 
  

   have 
  grown 
  down 
  into 
  the 
  bread, 
  and 
  if 
  one 
  could 
  see 
  through 
  

   the 
  bread 
  after 
  mold 
  has 
  grown 
  on 
  it 
  for 
  a 
  few 
  days, 
  much 
  

   of 
  the 
  mycelium 
  would 
  be 
  seen 
  within 
  it. 
  Branching 
  down- 
  

   ward 
  from 
  some 
  of 
  the 
  superficial 
  hyphre 
  are 
  special 
  root-like 
  

   hypha- 
  (rhizoids} 
  (fig. 
  184), 
  which 
  descend 
  and 
  spread 
  within 
  

   the 
  nutrient 
  material. 
  At 
  such 
  places 
  upright 
  hyplue 
  also 
  

   are 
  formed. 
  Long, 
  runner-like 
  branches 
  ( 
  ,sYA^x) 
  may 
  extend 
  

   over 
  the 
  surface 
  a 
  little 
  way. 
  From 
  the 
  stolons 
  a 
  new 
  set 
  of 
  

   rhizoids 
  and 
  upright 
  hypljju 
  may 
  grow. 
  

  

  