Annual  Report  for  1910  of  the  Botanist.  313 
A few  of  the  more  interesting  are  described  below,  with,  where 
practicable,  methods  for  dealing  with  them. 
Silver-leaf  on  Black  Currant. — This  disease  is  met  with 
very  commonly  on  various  kinds  of  plums,  particularly  the 
Victoria  plum.  It  occurs  occasionally  on  apples,  and  has  been 
reported  lately  on  gooseberries.  Its  presence  is  recognised 
with  certainty  by  the  characteristic  silvery  appearance  of  the 
foliage.  The  silvering  may  be  found  on  isolated  branches,  or 
the  whole  of  the  leaves  may  be  affected.  As  a rule  the  trees  die 
gradually,  and  on  the  dead  branches  and  trunks  the  fruiting 
stage  of  the  fungus  Stereurn  purpureum  may  occasionally  be 
met  with. 
It  has  been  suggested  that  a cure  may  be  effected  by  intro- 
ducing a solution  of  ferrous  sulphate  into  bore  holes  in  the 
trunks.  The  method  does  not  give  satisfactory  results,  and 
the  best  course  is  to  remove  infected  trees  as  speedily  and  as 
thoroughly  as  possible  and  destroy  them  by  burning. 
Gooseberries. — A few  specimens  supposed  to  be  attacked 
by  the  American  gooseberry  mildew  were  sent  for  examination. 
In  one  of  these  the  foliage  was  attacked  by  the  European 
mildew  ( Microsphcera  grossularice)  ; in  the  others  the  effects 
of  the  American  mildew  were  approximately  simulated  by  the 
attacks  of  aphis. 
The  disease  is  now  generally  distributed  in  this  country, 
and  in  view  of  its  importance  members  are  advised  to  take 
steps  to  eradicate  it  if  it  should  appear  amongst  their  planta- 
tions. 
In  the  early  stages  of  the  attack,  soon  after  the  foliage  is  fully 
expanded,  the  young  tips  of  the  twigs  become  covered  with  a 
white  coating  of  the  fungus,  from  which  myriads  of  spores 
capable  of  spreading  the  disease  are  produced.  At  this  stage 
spraying  with  a dilute  solution  of  liver  of  sulphur  containing 
one  half  of  an  ounce  to  a gallon  of  water,  if  repeated  at 
fortnightly  intervals,  will  do  much  to  suppress  the  disease. 
As  the  season  advances  the  white  coating  becomes  a rich 
brown  colour,  and  at  this  stage  a crop  of  resting  spores  is 
produced.  Twigs  showing  this  symptom  should  be  pruned 
off  and  burnt,  as  then  the  majority  of  the  resting  spores  will 
be  destroyed.  It  does  not  appear  to  be  advisable  to  prune 
before  the  middle  of  August.  If  the  operation  is  carried  out 
earlier,  buds,  which  would  normally  remain  dormant,  break 
and  give  rise  to  rapidly-grown,  succulent  wood,  which  is  very 
readily  infected.  Pruning,  however,  should  not  be  delayed 
beyond  the  end  of  August,  for  cases  have  been  met  with 
recently  where  the  fungus  has  attacked  the  foliage  as  well  as 
the  twigs  and  berries.  If  such  infected  leaves  are  allowed 
to  fall  to  the  ground  a crop  of  resting  spores  is  allowed  to 
