448 
Observations  on  Parasitic  Fungi. 
upper  part  of  the  plant  bends  down  at  this  point  and  dies,  as  I 
have  endeavoured  to  represent,  the  lower  portion  soon  following. 
The  leaves,  when  attacked,  turn  yellow  and  die,  and  the  slender 
pedicels  suffer  in  the  same  manner  as  the  stems,  falling  off  and 
leaving  the  racemes  nearly  naked.  The  roots  are  sound  at  the 
time,  and  the  plants  previously  to  the  attack  appear  in  the  highest 
state  of  luxuriance;  not  the  slightest  doubt  therefore  can  exist 
that  the  ftuldew  produces  the  gangrene  in  this  case,  and  not  the 
gangrene  the  mildew ; and  so  far  from  this  being  a rare  occur- 
rence, it  is  quite  the  reverse ; and  I speak  literally  when  I say 
that  cartloads  of  such  specimens  might  have  been  procured  in 
my  neighbourhood  in  1848-9,  and  I have  seen  a great  deal  this 
season. 
Uredo  Candida  (B.  2)  attacks  the  silicles  as  well  as  the  stems 
and  leaves,  growing  immediately  beneath  the  epidermis,  to  which 
it  gives  the  appearance  of  fine  white  enamel : at  length  this 
bursts,  and  the  tumour  is  found  to  be  filled  with  large  white 
globular  sporidia.  When  this  completely  envelopes  the  stems, 
as  it  frequently  does,  the  upper  part  of  the  plant  dies. 
I think  the  cases  to  which  I have  referred,  and  of  which  I 
have  preserved  specimens,  are  sufficient  to  satisfy  any  impartial 
mind  that  plants  even  of  native  growth  may  be  destroyed  by  the 
attacks  of  parasitic  fungi,  although  previously  in  perfect  health  ; 
at  least  they'  have  afforded  the  fullest  conviction  to  my  own  mind, 
notwithstanding  at  one  time  I entertained  a contrary  opinion. 
Many  persons  I know,  who  at  one  time  laughed  at  the  idea  of 
the  ‘Fungus  theory,’  as  it  was  termed,  have  entertained  very 
different  sentiments  after  inspecting  their  own  vineries.  Such 
are  the  ways  by  which  the  Creator  of  all  things  informs  mankind 
that  they  must  not  despise  even  the  least  of  His  works,  which 
are  as  beautiful  and  perfect  in  their  generation  as  man  in  his. 
I will  now,  for  the  sake  of  comparison,  shortly  describe  the 
modus  operandi  of  the  Botrytis  infestans  (fig.  9).  At  first,  a 
few  plants  of  it  appear  on  the  underside  of  the  leaves  of  the 
potato ; beneath  which  a dull  spot  ensues,  like  a bruise ; sur- 
rounding this  spot  a greyish  margin  is  seen,  and  the  part  within 
assumes  a darker  colour ; being,  in  fact,  dead — the  grey  margin 
ilenoting  where  the  fungus  is  growing  ; and  the  inner  spot  where 
it  has  done  its  work  and  passed  away  ; and  if  the  weather  has 
been  bright  and  windy  not  a trace  of  it  can  be  found  either  on 
that  or  the  adjoining  green  portion  of  the  leaf,  as  it  cannot  live  if 
exposed  to  a brisk  air,  but  spreads  rapidly  in  dull  gloomy  wea- 
ther. Scattered  plants  may  also  be  found  on  the  stems,  and,  at 
times,  in  shaded  situations  even  dense  grey  tults  are  perceptible 
bv  the  naked  eye,  beneath  which  the  dull  gangrenous  blotch 
alwavs  ensues;  which  infects  the  circulation  of  the  plant,  and 
