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  vegetative 
  stage 
  later 
  sends 
  up 
  in 
  various 
  ways 
  a 
  mass 
  of 
  tissue 
  which 
  

   results 
  in 
  the 
  formation 
  of 
  pustules. 
  These 
  appear 
  on 
  the 
  surface, 
  

   sometimes 
  more 
  or 
  less 
  regularly 
  rounded, 
  sometimes 
  rather 
  irregular. 
  

   In 
  the 
  case 
  of 
  the 
  summer 
  spore 
  stage, 
  we 
  have 
  inside 
  the 
  pustules 
  a 
  

   mass 
  of 
  tissue 
  which 
  is 
  formed 
  into 
  spores. 
  The 
  interior 
  of 
  the 
  spore 
  

   mass, 
  or 
  at 
  least 
  portions 
  of 
  it, 
  is 
  somewhat 
  nuicilaginous, 
  so 
  that 
  when 
  

   moisture 
  is 
  applied 
  a 
  swelling 
  of 
  the 
  interior 
  mass 
  is 
  produced 
  at 
  a 
  

   certain 
  stage 
  and 
  something 
  has 
  to 
  break. 
  As 
  a 
  result, 
  we 
  have 
  a 
  

   mucilaginous 
  mass 
  pressed 
  out 
  through 
  the 
  break 
  in 
  the 
  shape 
  of 
  a 
  

   twisted 
  thread, 
  much 
  the 
  same 
  as 
  if 
  you 
  take 
  a 
  collapsible 
  tube 
  of 
  paste 
  

   and 
  pinch, 
  it. 
  

  

  Xow, 
  one 
  of 
  those 
  summer 
  spore 
  threads 
  may 
  contain 
  anywhere 
  

   from 
  one 
  to 
  five 
  million 
  spores. 
  I 
  have 
  tried 
  to 
  estimate 
  the 
  number 
  in 
  

   a 
  thread 
  of 
  this 
  sort 
  which 
  was 
  about 
  an 
  eighth 
  of 
  an 
  inch 
  long, 
  and 
  by 
  

   taking 
  a 
  certain 
  portion 
  of 
  that 
  thread, 
  mounting 
  it 
  in 
  a 
  drop 
  of 
  water, 
  

   and 
  then 
  counting 
  over 
  a 
  certain 
  measured 
  area 
  under 
  the 
  microscope, 
  

   I 
  have 
  estimated, 
  by 
  multiplying, 
  that 
  there 
  were 
  2,400,000 
  spores 
  in 
  

   that 
  one 
  thread. 
  So 
  you 
  can 
  imagine 
  how 
  many 
  of 
  these 
  spores 
  may 
  be 
  

   produced 
  by 
  a 
  single 
  diseased 
  area 
  which 
  has 
  produced 
  perhaps 
  four 
  

   or 
  five 
  hundred 
  of 
  those 
  pustules, 
  each 
  pustule 
  containing 
  anywhere 
  

   from 
  one 
  to 
  twenty 
  threads. 
  Each 
  one 
  of 
  those 
  spores 
  may 
  develop 
  a 
  

   new 
  diseased 
  area, 
  provided 
  it 
  is 
  transported 
  to 
  a 
  fresh 
  break 
  in 
  the 
  

   bark 
  of 
  a 
  chestnut 
  tree. 
  Fortunately, 
  only 
  a 
  very 
  small 
  fraction 
  of 
  one 
  

   per 
  cent 
  ever 
  reaches 
  the 
  proper 
  place 
  for 
  growth. 
  

  

  This 
  last 
  is 
  what 
  I 
  alluded 
  to 
  as 
  the 
  summer 
  spore 
  stage. 
  There 
  is 
  

   a 
  winter 
  spore 
  stage, 
  or 
  technically, 
  the 
  ascospore 
  stage, 
  which 
  comes, 
  

   as 
  a 
  rule, 
  later 
  in 
  the 
  development 
  of 
  the 
  fungus. 
  In 
  this 
  same 
  pustule, 
  

   later 
  in 
  the 
  season, 
  certain 
  sacs 
  are 
  formed. 
  These 
  have 
  long 
  necks 
  

   which 
  extend 
  to 
  the 
  top 
  of 
  the 
  pustule. 
  These 
  sacs 
  are 
  sufficiently 
  large 
  

   to 
  be 
  seen 
  with 
  the 
  naked 
  eye. 
  They 
  are 
  dark 
  colored. 
  Inside 
  these, 
  we 
  

   have 
  a 
  lot 
  of 
  smaller 
  transparent 
  sacs 
  or 
  cases 
  in 
  each 
  of 
  which 
  we 
  get 
  

   eight 
  spores, 
  sometimes 
  in 
  one 
  row, 
  sometimes 
  in 
  two 
  rows. 
  Each 
  spore 
  

   can 
  propagate 
  the 
  fungus. 
  

  

  We 
  have, 
  then, 
  two 
  types 
  of 
  spores, 
  either 
  one 
  of 
  which 
  can 
  repro- 
  

   duce 
  the 
  fungus 
  under 
  suitable 
  conditions. 
  There 
  is 
  still 
  another 
  way 
  

   by 
  which 
  the 
  disease 
  may 
  be 
  kept 
  going. 
  The 
  vegetative 
  stage 
  can 
  sur- 
  

   vive 
  the 
  winter 
  and 
  continue 
  growing 
  the 
  following 
  year. 
  

  

  I 
  will 
  say 
  right 
  here 
  that 
  I 
  am 
  planning 
  to 
  give 
  you 
  merely 
  an 
  

   outline 
  of 
  this 
  disease, 
  and 
  have 
  time 
  afterwards 
  for 
  questions 
  which 
  I 
  

   think 
  in 
  a 
  meeting 
  of 
  this 
  sort 
  are 
  one 
  of 
  the 
  most 
  productive 
  sources 
  of 
  

   information. 
  

  

  In 
  regard 
  to 
  the 
  rapidity 
  of 
  spread 
  of 
  this 
  disease, 
  I 
  will 
  merely 
  

   call 
  your 
  attention 
  to 
  two 
  cases 
  as 
  illustrations, 
  or 
  to 
  certain 
  facts, 
  

  

  