446 
Observations  on  Parasitic  Fungi. 
and  young-  shoots ; and  wherever  it  appears,  the  parts  beneath  it 
always  turn  brown.  The  verbena  and  other  half-hardy  plants 
are  also  frequently  killed  by  it ; many  of  those  above  mentioned 
being  simultaneously  infested  by  Erysiphe  communis  (IT)  as  be- 
fore alluded  to.  This  commences  in  small  glossy  yellow  globules 
which  turn  brown  when  mature;  they  are  attached  to  the  plants 
by  their  own  independent  fulcra,  and  have  no  natural  connexion 
with  the  Oidium.  Dr.  Greville  supposed  that  the  peridia,  or  re- 
ceptacles of  the  spores,  burst  in  a circular  orifice  in  order  to  emit 
them;  but  on  subjecting  them  to  pressure,  which  I think  the  most 
likely  means  of  discovering  their  natural  mode  of  deshiscence,  I 
have  always  found  them  split  from  the  top  downwards;  the  spores 
being  contained  in  a few  transparent  sacs,  which  also  easily  burst. 
The  haulm  of  the  blue  pea  is  often  clothed  with  Botrytis 
vicim  (fig.  6),  which  invariably  kills  it.  The  tare  plant  is  fre- 
quently attacked  by  the  same  species,  and  in  1848  I observed 
several  patches  die  off  suddenly  under  this  visitation,  the  roots 
and  lower  parts  being,  however,  at  the  same  time  in  an  un- 
healthy condition,  apparently  from  too  much  wet.  Dark  blotches 
arise  also  both  on  the  stems  of  this  plant  and  the  bean,  suc- 
ceeded by  Botrytis  vulgaris  (fig.  10),  which,  however,  is  seldom 
found  on  the  living,  healthy  portions  of  any  plant. 
The  leaves  of  parsnips  during  the  two  past  years  have  been 
nearly  covered  with  large  white  patches  of  Botrytis  ganglioni- 
formis  (fig.  7),  which  produced  brown  blotches  and  soon  killed 
them,  the  mildew  being  quickly  dispersed  after  it  attains  maturity, 
so  that  no  one  examining  the  leaves  after  the  white  spots  were 
gone  would  be  able  to  detect  the  cause  of  their  decay.  In  this 
respect  they  bear  a close  resemblance  to  the  leaves  of  diseased 
potatoes.  The  roots  were  sound,  which  seems  to  show  that  they 
contain  some  antiseptic  property  in  a higher  degree  than  the 
potato  ; yet  it  has  been  recorded  in  the  Gardener’s  Chronicle 
that  the  roots  have  also  been  diseased  in  a similar  manner. 
Young  lettuce  plants  frequently  suffer  from  the  same  species 
of  Botrytis,  and,  if  thickly  planted,  it  soon  thins  them  most 
effectually. 
The  top  shoots  of  the  wallflower  are  likewise  attacked  by  this 
species,  which  gives  them  a swollen,  gouty  character,  and  ulti- 
mately kills  them. 
Having  thus  far  briefly  noticed  the  injurious  effects  of  a few 
species  of  parasitic  fungi  on  plants  chiefly  of  exotic  origin,  some- 
times causing  a diminution  of  produce,  in  other  cases  a premature 
decay  of  the  parts  attacked,  and  eventually  the  destruction  of 
the  entire  plants,  I will  now  relate  the  effects  produced  by  similar 
agents  on  several  hardy,  indigenous  weeds. 
The  common  plantain  has  been  covered  with  Oidium  com- 
