﻿244 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  temperature 
  it 
  develops 
  in 
  a 
  very 
  short 
  time, 
  growing 
  by 
  

   means 
  of 
  food 
  material 
  that 
  has 
  been 
  gathered 
  by 
  the 
  under- 
  

   ground 
  growth. 
  In 
  the 
  deep, 
  wrinkle-bordered 
  pits 
  of 
  the 
  

  

  mushroom 
  are 
  the 
  spore- 
  

   bearing 
  hyplue. 
  The 
  spores 
  

   form 
  in 
  great 
  numbers; 
  

   they 
  are 
  very 
  light 
  and 
  are 
  

   easily 
  carried 
  long 
  distances 
  

   by 
  currents 
  of 
  air. 
  Most 
  

   of 
  the 
  mushrooms 
  do 
  not 
  

   belong 
  to 
  the 
  Axf<>nt//<-ffi'x. 
  

   232. 
  Lilac 
  mildew. 
  Mil- 
  

   dews 
  are 
  frequently 
  found 
  

   upon 
  (lie 
  surface 
  of 
  leaves 
  

   of 
  lilac 
  (tig. 
  100") 
  and 
  

   upon 
  the 
  willow, 
  oak, 
  some 
  

   of 
  the 
  smartweeds, 
  and 
  

   many 
  other 
  plants. 
  The 
  

   fungus 
  is 
  a 
  superficial 
  

   parasite 
  with 
  haustoria 
  

   penetrating 
  the 
  host 
  cells. 
  

   At 
  times 
  upright 
  hyphre 
  form 
  conidia, 
  and 
  to 
  their 
  presence 
  

   the 
  powdery 
  appearance 
  of 
  these 
  mildews 
  is 
  largely 
  clue. 
  The 
  

   conidia, 
  if 
  favorably 
  placed, 
  are 
  the 
  means 
  of 
  producing 
  new 
  

  

  FIG. 
  190. 
  Lilac 
  mildew 
  

  

  A, 
  leaves 
  of 
  lilac 
  upon 
  which 
  lilac 
  mildew 
  

   appears 
  in 
  whitish 
  patches; 
  the 
  small, 
  dark 
  

   reproductive 
  bodies 
  are 
  also 
  shown. 
  />', 
  the 
  

   central, 
  heavy-walled 
  body 
  (ascocarp) 
  which 
  

   contains 
  the 
  sacs 
  (asci) 
  in 
  which 
  spores 
  are 
  

   formed. 
  Upon 
  the 
  wall 
  of 
  the 
  ascocarp 
  are 
  

   stalks, 
  sometimes 
  called 
  arms, 
  which 
  have 
  

   peculiar 
  branches 
  at 
  their 
  tips. 
  About 
  60 
  

   times 
  natural 
  size 
  

  

  