﻿i?ROCEEDINGS 
  OF 
  THE 
  FOURTH 
  ENTOMOLOGICAL 
  MEETING 
  57 
  

  

  shut 
  up 
  by 
  the 
  pest, 
  were 
  growing 
  through 
  the 
  attack 
  without 
  being 
  

   touched. 
  Leaf 
  was 
  plucked 
  from 
  these 
  bushes 
  and 
  analysed, 
  when 
  it 
  

   was 
  found, 
  in 
  all 
  cases, 
  that 
  the 
  ratio 
  of 
  potash 
  to 
  phosphoric 
  acid 
  in 
  

   the 
  leaf 
  was 
  4 
  to 
  1. 
  Since 
  the 
  normal 
  ratio 
  is 
  2 
  to 
  1, 
  it 
  is 
  plain 
  that 
  

   the 
  throwing 
  off 
  of 
  the 
  pest 
  is 
  connected 
  with 
  a 
  distinct 
  increase 
  in 
  

   the 
  potash 
  in 
  the 
  leaf 
  as 
  compared 
  with 
  the 
  phosphoric 
  acid, 
  which 
  

   corroborates 
  previous 
  ideas. 
  

  

  The 
  state 
  of 
  affairs, 
  then, 
  before 
  the 
  carrying 
  out 
  of 
  the 
  experiments 
  

   about 
  to 
  be 
  referred 
  to, 
  was 
  that 
  there 
  was 
  a 
  considerable 
  amount 
  of 
  

   evidence 
  to 
  show 
  that 
  an 
  increase 
  in 
  the 
  ratio 
  of 
  potash 
  to 
  phosphoric 
  

   acid 
  in 
  the 
  leaf 
  produced 
  increased 
  resistance 
  to 
  Helopeltis 
  attack 
  and 
  

   that 
  experiments 
  designed 
  to 
  increase 
  that 
  ratio 
  by 
  the 
  addition 
  of 
  potash 
  

   to 
  the 
  soil 
  had 
  given 
  results 
  which, 
  though 
  positive 
  in 
  a 
  few 
  cases, 
  were 
  

   contradictory 
  to 
  others. 
  The 
  obvious 
  experiment 
  to 
  perform 
  was 
  that 
  

   of 
  direct 
  injection 
  of 
  the 
  bushes 
  with 
  potash, 
  so 
  as 
  to 
  eliminate 
  the 
  dis- 
  

   turbing 
  influence 
  of 
  the 
  soil 
  factors. 
  This 
  had 
  been 
  tried, 
  but 
  unsuccess- 
  

   fully. 
  At 
  the 
  last 
  meeting 
  I 
  d'scussed 
  this 
  work 
  with 
  Dr. 
  Gough 
  and 
  he 
  

   made 
  various 
  suggestions 
  with 
  regard 
  to 
  the 
  injection 
  of 
  the 
  bushes 
  by 
  

   way 
  of 
  the 
  roots. 
  After 
  a 
  certain 
  amount 
  of 
  experiment 
  I 
  found 
  that 
  if 
  

   a 
  number 
  of 
  the 
  feeding 
  roots 
  were 
  placed 
  into 
  a 
  solution 
  of 
  a 
  soluble 
  

   salt 
  of 
  potash 
  this 
  solution 
  was 
  taken 
  up, 
  and 
  in 
  1919 
  we 
  were 
  successful, 
  

   on 
  one 
  garden, 
  in 
  causing 
  bushes 
  which 
  were 
  black 
  with 
  " 
  mosquito 
  

   blight 
  " 
  to 
  throw 
  off 
  the 
  attack 
  of 
  the 
  pest 
  and 
  give 
  strong 
  clean 
  flushes 
  

   to 
  the 
  end 
  of 
  the 
  season. 
  During 
  the 
  last 
  season 
  the 
  experiments 
  were 
  

   repeated 
  on 
  a 
  larger 
  scale, 
  in 
  all 
  the 
  affpcted 
  districts, 
  and 
  on 
  different 
  

   types 
  of 
  sofl, 
  more 
  than 
  eleven 
  hundred 
  bushes 
  being 
  treated 
  in 
  Assam, 
  

   Cachar, 
  Sylhet, 
  and 
  the 
  Duars. 
  It 
  is 
  to 
  be 
  regretted 
  that 
  circumstances 
  

   compefled 
  me 
  to 
  postpone 
  my 
  final 
  tour 
  of 
  inspection 
  of 
  the 
  experiments 
  

   until 
  January, 
  with 
  the 
  result 
  that 
  I 
  have 
  not 
  yet 
  had 
  time 
  to 
  work 
  out 
  

   the 
  results 
  as 
  thoroughly 
  as 
  I 
  wish. 
  Two 
  significant 
  points, 
  however, 
  

   stand 
  out. 
  The 
  first 
  is 
  that 
  the 
  only 
  substance 
  which 
  has 
  produced 
  

   increased 
  resistance 
  to 
  attack 
  is 
  potash, 
  the 
  second 
  is, 
  that 
  attempts 
  to 
  

   increase 
  the 
  liability 
  to 
  attack 
  appear 
  to 
  have 
  fafled. 
  The 
  percentage 
  of 
  

   experiments 
  which 
  worked 
  satisfactorily 
  was 
  small, 
  owing 
  partly 
  to 
  the 
  

   fact 
  that 
  some 
  of 
  the 
  substances 
  used 
  were 
  unsuitable, 
  and 
  partly 
  to 
  lack 
  

   of 
  experience 
  of 
  work 
  of 
  this 
  kind. 
  The 
  most 
  satisfactory 
  strength 
  of 
  

   solution 
  to 
  use 
  was 
  found 
  to 
  be 
  a 
  half 
  to 
  one 
  per 
  cent. 
  The 
  method 
  

   of 
  carrying 
  out 
  of 
  the 
  experiment 
  was 
  as 
  foUows 
  : 
  A 
  small 
  root 
  or 
  a 
  

   bunch 
  of 
  small 
  roots 
  was 
  exposed, 
  freed 
  from 
  sofl, 
  and 
  immersed 
  in 
  a 
  

   cigarette 
  tin 
  containing 
  the 
  solution. 
  The 
  tin 
  was 
  then 
  fixed 
  firmly 
  

   in 
  position 
  by 
  ramming 
  the 
  soil 
  round 
  it, 
  covered 
  with 
  strong 
  paper 
  to 
  

   prevent 
  sofl 
  from 
  falling 
  into 
  it, 
  and 
  the 
  excavated 
  soil 
  put 
  carefully 
  

  

  