Report  on  Wheat-Mildew. 
643 
here  was  a plant  which  is  tolerably  common  in  gardens,  and  it 
had  never  been  suspected  of  having  taken  any  part  in  rearing 
this  parasite,  much  less  detected  in  the  very  act.  Indeed,  1 
have  been  told  of  a Norfolk  gentleman,  who  after  listening  to 
one  of  Mr.  Plowright’s  lectures  on  mildew,  went  home  in  great 
distress,  for  he  had  been  planting  barberries  largely,  without  any 
notion  that  he  might  have  been  contributing  to  agricultural 
distress  by  propagating  mildew.  With  very  great  regret  he 
sacrificed  his  shrubs,  and  was  afterwards  told  on  the  best  autho- 
rity that,  as  they  were  Bcrberis  aquifolium,  they  were  perfectly 
harmless.  If  one  cecidium-bearing  shrub  has  escaped  the 
notice  of  the  botanists,  why  not  others  ? Again,  barberries  are 
said  to  be  unknown  in  Australia,  but  mildew  is  found  there. 
Quite  recently  Mr.  Plowright  has  examined  specimens  of  straw 
sent  over  for  his  inspection  from  Queensland,  and  he  pronounces 
the  disease  to  be  Paccinia  graminis , and  he  writes  to  me  thus  : 
“ One  feels  inclined  to  think  that  there  must  be  some  CEcidium 
host  other  than  the  barberry.”  Taking  all  things  into  con- 
sideration, it  does  seem  not  improbable  that  some  other  plant 
may  take  the  place  of  the  barberry.  It  is  perhaps  worth  while 
to  mention  that  there  are  some  who  affirm  that  the  elder-tree 
will  produce  mildew,  and  who  assert,  as  confidently  as  ever  the 
advocates  of  the  barberry  theory  have  done,  that  they  have 
traced  the  disease  to  some  bush  of  this  description,  and  that 
they  have  seen  lines  of  mildew  starting  from  one,  just  as  they 
are  said  to  have  done  from  barberry-trees.  At  present,  the 
most  careful  search  amongst  the  leaves  of  the  elder  has  not  been 
rewarded  with  any  success. 
But  on  the  second  point,  as  to  the  fungus  maintaining  life 
for  more  than  one  season  without  resorting  to  the  barberry,  a 
new  light  has  been  thrown  by  Mr.  Plowright.  It  has  been 
said  above  that  the  mycelium  in  wheat,  8cc.,  produces  Uredo- 
spores  until  the  host-plant  approaches  maturity.  Now  if  these 
Uredo-spores  can  find  a succession  of  suitable  plants  in  a growing 
state,  successive  generations  of  Uredo-spores  will  be  produced 
throughout  the  winter.  In  December  1881  Mr.  Plowright  found 
a fresh  pustule  of  Uredo  upon  Twitch  grass,  and  in  January 
1883,  he  sent  me  similar  specimens  which  he  had  recently 
gathered.  He  also  informs  me  that  he  has  proved  that  the 
Uredo  of  Paccinia  rubigo  vera , a species  nearly  allied  to 
P.  graminis,  will  stand  a temperature  of  23°  Fahr.  without  injury 
to  its  vitality. 
But  Mr.  Plowright  goes  one  step  farther,  and  ventures  to 
assert  the  probability  that  the  Promycelium-spores  of  mildew 
have  the  power  of  entering  the  wheat-plant,  and  there  producing 
mycelium,  with  its  successive  stages  of  Uredo  and  Teleuto-spores, 
