﻿65 
  

  

  Foliage 
  Characteristics 
  

  

  The 
  character 
  of 
  the 
  foliage 
  varies 
  from 
  the 
  broad-leaved 
  types, 
  

   whose 
  foliage 
  somewhat 
  resembles 
  that 
  of 
  the 
  horse-chestnut, 
  to 
  

   the 
  narrow-leaved 
  varieties 
  whose 
  leaves 
  have 
  a 
  tendency 
  to 
  curl 
  

   up 
  like 
  the 
  foliage 
  of 
  the 
  Winesap 
  apple. 
  The 
  broad-leaved 
  types 
  

   are 
  much 
  more 
  densely 
  foliated 
  and 
  this 
  factor 
  has 
  considerable 
  

   bearing 
  on 
  the 
  problems 
  of 
  sun-scald 
  on 
  the 
  twigs 
  and 
  trunks 
  of 
  the 
  

   tree 
  and 
  the 
  exposure 
  of 
  the 
  nuts 
  to 
  this 
  injury. 
  For 
  this 
  reason, 
  

   the 
  densely 
  fohated 
  varieties 
  may 
  prove 
  best 
  adapted 
  to 
  the 
  inland 
  

   valleys, 
  where 
  the 
  difficulties 
  of 
  sun-scald 
  are 
  most 
  prevalent. 
  The 
  

   more 
  sparsely 
  foliated 
  types 
  often 
  appear 
  to 
  have 
  less 
  blight 
  on 
  

   the 
  nuts 
  and 
  leaves 
  because 
  of 
  their 
  exposure 
  to 
  the 
  sunshine. 
  

  

  Disease 
  Resistance 
  

  

  Probably 
  one 
  of 
  the 
  most 
  important 
  limiting 
  factors 
  in 
  walnut 
  

   production 
  in 
  California, 
  and 
  especially 
  in 
  the 
  older 
  walnut 
  sections, 
  

   is 
  the 
  bacterial 
  disease 
  commonly 
  known 
  as 
  walnut 
  blight. 
  The 
  

   inroads 
  of 
  this 
  disease 
  have 
  caused 
  a 
  very 
  heavy 
  dropping 
  of 
  the 
  

   nuts 
  during 
  many 
  seasons 
  of 
  the 
  past, 
  and 
  although 
  a 
  great 
  deal 
  

   of 
  time 
  and 
  scientific 
  effort 
  has 
  been 
  devoted 
  to 
  the 
  control 
  of 
  the 
  

   trouble, 
  there 
  is 
  no 
  satisfactory 
  known 
  means 
  for 
  the 
  prevention 
  of 
  

   walnut 
  blight 
  at 
  the 
  present 
  time. 
  

  

  It 
  is 
  a 
  well-known 
  fact 
  that 
  in 
  the 
  vegetable 
  kingdom 
  closely 
  

   related 
  species 
  suffer 
  in 
  different 
  degrees 
  from 
  the 
  attacks 
  of 
  the 
  

   same 
  parasite. 
  This 
  difference 
  in 
  resistance 
  is 
  often 
  as 
  marked 
  

   among 
  different 
  varieties 
  of 
  the 
  same 
  species 
  as 
  between 
  the 
  species 
  

   themselves. 
  The 
  absence 
  of 
  blight 
  is 
  not 
  necessarily 
  an 
  indication 
  

   • 
  of 
  immunity. 
  There 
  is 
  a 
  great 
  deal 
  of 
  difference 
  in 
  the 
  amount 
  of 
  

   blight 
  prevalent 
  at 
  the 
  present 
  season 
  in 
  the 
  different 
  walnut 
  

   growing 
  sections. 
  Again, 
  the 
  immunity 
  from 
  blight 
  of 
  a 
  particular 
  

   tree 
  for 
  one 
  season 
  may 
  be 
  followed 
  by 
  more 
  or 
  less 
  pre 
  valency 
  of 
  

   blight 
  on 
  the 
  same 
  tree 
  the 
  next 
  season. 
  The 
  degree 
  of 
  resistance 
  

   must 
  be 
  tested 
  out 
  through 
  a 
  number 
  of 
  years 
  before 
  any 
  variety 
  

   can 
  be 
  pronounced 
  resistant 
  to 
  this 
  disease. 
  The 
  observations 
  

   must 
  also 
  be 
  carried 
  out 
  in 
  different 
  localities 
  as 
  certain 
  varieties 
  

   seem 
  to 
  behave 
  differently 
  on 
  different 
  soils 
  and 
  when 
  growing 
  under 
  

   different 
  climatic 
  conditions. 
  

  

  Some 
  varieties 
  seem 
  to 
  avoid 
  the 
  blight 
  the 
  majoritj^ 
  of 
  the 
  seasons 
  

   but 
  really 
  have 
  little 
  or 
  no 
  resistant 
  qualities 
  when 
  the 
  seasonal 
  

   conditions 
  and 
  the 
  growth 
  of 
  the 
  plant 
  happen 
  to 
  coincide 
  with 
  the 
  

   most 
  favorable 
  time 
  for 
  the 
  spread 
  of 
  the 
  disease. 
  An 
  example 
  of 
  

   this 
  is 
  seen 
  in 
  the 
  Eureka 
  variety 
  the 
  present 
  season. 
  While 
  this 
  

  

  5 
  

  

  