﻿LABORATORY 
  OBSERVATIONS 
  AND 
  EXPERIMENTS. 
  27 
  

  

  conidiophore. 
  The 
  average 
  diameter 
  of 
  20 
  spores 
  was 
  2.3 
  micromillimeters. 
  

   It 
  is 
  by 
  means 
  of 
  these 
  minute 
  spores 
  that 
  the 
  fungus 
  is 
  so 
  rapidly 
  dissemin- 
  

   ated 
  throughout 
  a 
  field 
  infested 
  with 
  chinch-bugs. 
  The 
  spores 
  are 
  capable 
  of 
  

   germination 
  as 
  soon 
  as 
  formed, 
  and 
  under 
  favorable 
  conditions, 
  such 
  as 
  exist 
  

   in 
  the 
  humid 
  atmosphere 
  of 
  a 
  culture 
  chamber, 
  a 
  new 
  crop 
  of 
  spores 
  may 
  be 
  

   produced 
  within 
  three 
  days. 
  In 
  sterilized 
  beef 
  broth 
  the 
  spores 
  do 
  not 
  al- 
  

   ways 
  germinate 
  into 
  a 
  branched 
  mycelium, 
  but 
  frequently 
  begin 
  a 
  process 
  of 
  

   budding 
  which 
  is 
  apparently 
  indefinitely 
  continued. 
  This 
  is 
  shown 
  in 
  Plate 
  II, 
  

   figs. 
  3 
  to 
  7 
  inclusive. 
  The 
  conidial 
  spores 
  do 
  not 
  long 
  retain 
  their 
  vitality. 
  

   In 
  our 
  experience, 
  the 
  spores 
  were 
  unable 
  to 
  germinate 
  after 
  one 
  month, 
  when 
  

   kept 
  in 
  a 
  dry 
  atmosphere 
  ; 
  but 
  in 
  a 
  humid 
  atmosphere 
  the 
  spores 
  retained 
  

   their 
  power 
  of 
  germinating 
  for 
  over 
  two 
  months. 
  In 
  no 
  instance 
  could 
  spores 
  

   formed 
  in 
  July 
  be 
  made 
  to 
  germinate 
  in 
  October. 
  The 
  fungus 
  must 
  therefore 
  

   make 
  provision 
  for 
  its 
  self-preservation 
  during 
  protracted 
  periods 
  of 
  weather 
  

   unfavorable 
  to 
  the 
  development 
  of 
  conidial 
  spores. 
  Culture 
  plates 
  in 
  our 
  lab- 
  

   oratories 
  covered 
  with 
  pure 
  cultures 
  of 
  Sporotrichum, 
  planted 
  on 
  a 
  gelatine 
  

   plate 
  July 
  9, 
  show 
  in 
  autumn 
  and 
  winter 
  the 
  mycelial 
  branches 
  within 
  the 
  

   culture 
  medium 
  swollen 
  at 
  intervals 
  to 
  a 
  diameter 
  of 
  3.9 
  to 
  8.8 
  micromilli- 
  

   meters 
  (Plate 
  II, 
  figs. 
  11 
  and 
  12), 
  the 
  average 
  diameter 
  of 
  the 
  unswollen 
  

   mycelial 
  branches 
  being 
  about 
  2.5 
  micromillimeters. 
  

  

  Conidial 
  spores 
  were 
  planted 
  in 
  a 
  drop 
  of 
  beef 
  broth 
  on 
  a 
  microscope 
  slide 
  

   kept 
  in 
  a 
  moist 
  chamber, 
  and 
  after 
  the 
  fungus 
  had 
  developed 
  to 
  the 
  forma- 
  

   tion 
  of 
  spores, 
  the 
  chamber 
  was 
  permitted 
  to 
  slowly 
  become 
  dry. 
  Mycelial 
  

   bodies 
  were 
  formed 
  similar 
  to 
  those 
  on 
  the 
  culture 
  plate. 
  The 
  culture 
  was 
  

   then 
  divided 
  and 
  one 
  portion 
  was 
  transferred 
  to 
  beef 
  broth 
  on 
  another 
  slide, 
  

   and 
  the 
  beef 
  broth 
  was 
  then 
  frozen 
  solid 
  by 
  the 
  evaporation 
  of 
  ether. 
  Both 
  

   slides 
  were 
  then 
  put 
  into 
  a 
  moist 
  chamber, 
  a 
  fresh 
  supply 
  of 
  beef 
  broth 
  being 
  

   added 
  to 
  the 
  original 
  slide. 
  The 
  mycelial 
  bodies 
  on 
  both 
  slides 
  had 
  put 
  out 
  

   germ 
  tubes 
  in 
  24 
  hours, 
  and 
  at 
  the 
  expiration 
  of 
  a 
  week 
  aerial 
  conidia 
  were 
  

   formed, 
  ellipsoidal, 
  and 
  borne 
  in 
  chains 
  on 
  simple 
  or 
  verticillate 
  branches, 
  

   and 
  measuring 
  from 
  5.8x2.9 
  to 
  7.8x3.9 
  micromillimeters. 
  At 
  this 
  stage 
  of 
  its 
  

   existence, 
  the 
  fungus 
  bears 
  a 
  striking 
  resemblance 
  to 
  the 
  genus 
  Cordyceps. 
  

   Chinch-bugs 
  which 
  died 
  of 
  Sporotrichum 
  during 
  the 
  summer, 
  and 
  six 
  months 
  

   later 
  are 
  still 
  enveloped 
  with 
  the 
  characteristic 
  growth 
  of 
  that 
  fungus, 
  when 
  

   put 
  into 
  a 
  moist 
  chamber 
  become 
  covered 
  in 
  a 
  few 
  days 
  with 
  a 
  growth 
  of 
  the 
  

   Cordyceps 
  type. 
  The 
  new 
  growth 
  is 
  at 
  first 
  white, 
  but 
  turns 
  pink 
  when 
  old. 
  

   The 
  spores 
  of 
  this 
  new 
  growth, 
  when 
  planted 
  in 
  beef 
  broth, 
  reproduce 
  forms 
  

   like 
  themselves 
  ; 
  but 
  the 
  body 
  of 
  the 
  fungus 
  remains 
  white. 
  We 
  have 
  not 
  

   yet 
  observed 
  the 
  reversion 
  from 
  the 
  Cordyceps 
  type 
  back 
  to 
  Sporotrichum. 
  

  

  Resting 
  spores 
  are 
  also 
  found 
  on 
  the 
  gelatine 
  culture 
  plates, 
  having 
  a 
  di- 
  

   ameter 
  of 
  20 
  micromillimeters, 
  and 
  a 
  thickness 
  of 
  cell 
  wall 
  of 
  1.8 
  micromilli- 
  

   meters 
  (Plate 
  II, 
  fig. 
  13). 
  Similar 
  spores 
  are 
  found 
  in 
  the 
  crushed 
  bodies 
  

   of 
  chinch-bugs 
  covered 
  with 
  Sporotrichum. 
  While 
  it 
  was 
  found 
  that 
  pure 
  

   cultures 
  of 
  Sporotrichum 
  could 
  easily 
  be 
  obtained, 
  repeated 
  attempts 
  to 
  inocu- 
  

   late 
  chinch-bugs 
  from 
  these 
  pure 
  cultures 
  were 
  unsuccessful. 
  

  

  