Observations  on  Parasitic  Fungi. 
451 
I have  placed  portions  of  the  mildew  in  the  sap  of  the  plants 
on  which  it  grew  and  also  in  water,  both  of  which  have  a dark 
colour  imparted  to  them.  Not  being  acquainted  with  chemistry, 
1 submit  this  view  of  the  case  to  those  who  are  proficient  in  that 
science.  I think,  however,  that  as  all  traces  of  the  structure  of 
the  mildew  are  lost,  and  a brown  colour  imparted  to  the  sap  of 
the  plant  on  which  it  grew,  which  I have  more  than  once  proved, 
I may  reasonably  conclude  that  a similar  effect  is  produced  na- 
turally when  the  mildewed  plant  in  a state  of  nature  presents  the 
same  features. 
That  the  actual  disease  of  the  potato  is  of  a gangrenous  nature 
is  generally  admitted,  and  in  my  former  Essay  I was  of  opinion 
that  such  was  the  primary  cause  of  it.  That  gangrene  is  com- 
monly produced  on  plants  without  the  aid  of  fungi  I have  had 
abundant  evidence,  and  I am  quite  confident  Botrytis  infestans  was 
not  present  (at  least  externally)  on  those  plants  on  which  I made 
the  experiments  described  in  my  former  Essay  ; and  from  which, 
owing  to  the  limited  time  of  sending  it  in,  I was  obliged  to 
draw  my  conclusions.  As  almost  every  statement  therein  was 
the  result  of  my  own  observation,  I do  not  wish  to  withdraw  any 
portion,  except  such  matters  of  opinion  as  are  at  variance  with 
the  experience  which  I have  since  acquired  of  the  power  of  para- 
sitic fungi. 
Close  observation  of  these  tyrants  of  the  vegetable  kingdom 
for  the  last  four  years  has  convinced  me  that  the  gangrene  of  the 
potato  is  produced  by  the  mildew,  Botrytis  infestans,  and  that  I 
was  previously  in  error  in  supposing  that  the  Botrytis  was  the 
result  of  the  gangrene.  The  minute  Oidium  setarum  certainly 
does  not  produce  the  disease  on  the  tubers,  and  though  instances 
may  occur  of  these  being  diseased  previously  to  the  haulm  being 
attacked  by  Botrytis,  I am  of  opinion  that  such  cases  are  by  no 
means  common.  No  sort  escapes  its  attack  ; but  with  me,  that 
called  farmer's  profit,  has  produced  the  largest  and  by  far  the 
soundest  crops. 
As  the  term  "potato  disease”  is  a very  vague  expression,  and 
there  is  no  word  in  common  use  which  embraces  the  class  of 
diseases  which  may  now  be  fairly  referred  to  the  action  of  fungi, 
I beg  to  propose  the  name  “ Mycopathy  ” for  such  injuries  as  I 
have  shown  frequently  arise  from  them. 
I have  much  pleasure  in  thus  adding  my  humble  testimony  in 
support  of  the  view  taken  of  this  subject  by  the  Rev.  M.  J. 
Berkeley,  who  from  his  previous  studies  was  so  well  qualified  to1 
form  a correct  opinion  upon  it. 
Cranford,  August  22nd,  1850. 
