﻿CHAPTER 
  XVI 
  

  

  FUNGI 
  AND 
  FUNGOUS 
  DISEASES 
  OF 
  PLANTS 
  

  

  220. 
  The 
  fungi 
  as 
  dependent 
  plants. 
  In 
  our 
  earlier 
  discus- 
  

   sion 
  of 
  plant 
  nutrition 
  it 
  was 
  found 
  that 
  green 
  plants 
  possess 
  

   chlorophyll, 
  by 
  means 
  of 
  which 
  they 
  make 
  their 
  own 
  foods. 
  

   Every 
  observant 
  person 
  who 
  has 
  had 
  any 
  considerable 
  experi- 
  

   ence 
  with 
  plants 
  has 
  noted 
  several 
  or 
  many 
  kinds, 
  as 
  mush- 
  

   rooms 
  and 
  molds, 
  that 
  do 
  not 
  

   possess 
  chlorophyll. 
  These 
  

   chlorophyll-less 
  plants 
  can- 
  

   not 
  manufacture 
  foods 
  from 
  

   water 
  and 
  carbon 
  dioxide, 
  and 
  

   hence 
  are 
  dependent. 
  Their 
  

   dependence 
  appears 
  in 
  various 
  

   relations 
  between 
  them 
  and 
  

   the 
  host 
  plants 
  or 
  animals 
  

   that 
  supply 
  them 
  the 
  requi- 
  

   site 
  food. 
  Sometimes 
  they 
  live 
  

   upon 
  or 
  within 
  living 
  plants 
  

   or 
  animals, 
  being 
  known 
  as 
  

   jHtritxift'x 
  : 
  or 
  they 
  may 
  live 
  

   upon 
  dead 
  nutrient 
  sub- 
  

   stances, 
  when 
  they 
  are 
  known 
  

   as 
  saprophytes 
  (fig. 
  182). 
  

   There 
  are 
  many 
  common 
  fungous 
  parasites, 
  as 
  wheat 
  rust, 
  

   potato 
  blight, 
  and 
  tree-destroying 
  fungi. 
  Our 
  economic 
  crops 
  

   are 
  greatly 
  reduced 
  in 
  value 
  every 
  year 
  through 
  the 
  destruc- 
  

   tiveness 
  of 
  these 
  parasitic 
  plants. 
  Fungous 
  saprophytes 
  are 
  

   also 
  very 
  abundant, 
  the 
  best-known 
  being 
  molds, 
  mushrooms, 
  

   and 
  puff 
  balls. 
  In 
  almost 
  any 
  deeply 
  shaded, 
  moist, 
  and 
  warm 
  

  

  234 
  

  

  FIG. 
  182. 
  An 
  old 
  pine 
  stump 
  upon 
  

   which 
  the 
  fungus 
  Polyporus 
  is 
  growing 
  

  

  