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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1943 
  

  

  periods 
  of 
  years. 
  Such 
  efforts 
  continued 
  until 
  the 
  plantations 
  of 
  Para 
  

   rubber 
  trees 
  in 
  the 
  Malay 
  Peninsula 
  began 
  to 
  supply 
  the 
  market, 
  and 
  

   the 
  need 
  of 
  searching 
  further 
  for 
  wild 
  rubber 
  seemed 
  to 
  have 
  passed. 
  

  

  In 
  reality 
  the 
  commercial 
  surveys 
  had 
  taken 
  only 
  a 
  partial 
  view 
  of 
  

   the 
  general 
  problem 
  of 
  natural 
  rubber. 
  The 
  rubber-producing 
  plants 
  

   were 
  not 
  studied 
  or 
  evaluated 
  from 
  the 
  standpoint 
  of 
  agricultural 
  

   production 
  possibilities, 
  but 
  only 
  with 
  reference 
  to 
  their 
  existence 
  in 
  

   large 
  numbers 
  over 
  wide 
  areas, 
  in 
  sufficient 
  abundance 
  to 
  be 
  exploited 
  

   in 
  commercial 
  quantities. 
  No 
  commercial 
  interest 
  would 
  be 
  taken 
  in 
  

   trees 
  or 
  plants 
  limited 
  to 
  small 
  areas 
  or 
  occurring 
  as 
  rare, 
  widely 
  scat- 
  

   tered 
  individuals. 
  

  

  With 
  a 
  plant 
  that 
  is 
  brought 
  into 
  cultivation, 
  it 
  obviously 
  makes 
  

   little 
  difference 
  whether 
  the 
  wild 
  stock 
  is 
  scattered 
  widely 
  in 
  nature 
  

   or 
  limited 
  to 
  a 
  single 
  district, 
  or 
  even 
  to 
  a 
  single 
  locality. 
  Many 
  spe- 
  

   cies 
  are 
  localized, 
  especially 
  in 
  tropical 
  regions, 
  to 
  an 
  extent 
  that 
  is 
  

   seldom 
  appreciated. 
  The 
  apparent 
  uniformity 
  of 
  tropical 
  forests 
  al- 
  

   lows 
  us 
  to 
  suppose 
  that 
  the 
  same 
  species 
  are 
  widely 
  distributed, 
  but 
  

   even 
  where 
  forests 
  are 
  continuous 
  the 
  species 
  may 
  prove 
  to 
  vary. 
  

   Richard 
  Spruce, 
  after 
  several 
  years 
  of 
  intensive 
  exploration 
  in 
  the 
  

   Amazon 
  valley, 
  estimated 
  that 
  with 
  every 
  degree 
  of 
  latitude 
  half 
  of 
  

   the 
  species 
  were 
  changed. 
  

  

  Alfred 
  Russell 
  Wallace, 
  who 
  visited 
  Brazil 
  during 
  the 
  same 
  period 
  

   that 
  Spruce 
  did, 
  also 
  failed 
  to 
  distinguish 
  between 
  the 
  two 
  types 
  of 
  

   trees 
  that 
  were 
  being 
  exploited 
  in 
  the 
  Amazon 
  valley. 
  Even 
  in 
  1908, 
  

   in 
  publishing 
  Spruce's 
  Journals, 
  Wallace 
  writes 
  of 
  cutting 
  the 
  trees 
  

   down 
  as 
  a 
  method 
  of 
  utilization 
  that 
  had 
  been 
  applied 
  to 
  the 
  Para 
  

   rubber 
  in 
  the 
  early 
  days. 
  Wallace 
  held 
  that 
  the 
  latex 
  served 
  for 
  the 
  

   growth 
  of 
  the 
  trees 
  and 
  that 
  tapping 
  should 
  be 
  suspended 
  during 
  

   the 
  flowering 
  and 
  fruiting 
  season. 
  

  

  Several 
  species 
  of 
  Siphonia, 
  or 
  Hevea, 
  have 
  been 
  described 
  from 
  the 
  

   Amazon 
  valley, 
  but 
  only 
  one 
  species 
  of 
  Castilla. 
  The 
  number 
  of 
  per- 
  

   ceptibly 
  different 
  local 
  forms 
  of 
  Castilla 
  doubtless 
  would 
  run 
  into 
  

   scores 
  or 
  hundreds, 
  if 
  a 
  thorough 
  study 
  could 
  be 
  made. 
  Ten 
  species 
  

   were 
  distinguished 
  in 
  a 
  monograph 
  by 
  Pittier 
  published 
  in 
  1910, 
  and 
  

   others 
  may 
  be 
  described, 
  but 
  the 
  number 
  that 
  can 
  be 
  separated 
  and 
  

   classified 
  by 
  definite 
  differences 
  may 
  not 
  be 
  much 
  larger. 
  The 
  species 
  

   of 
  Castilla 
  are 
  less 
  localized 
  than 
  in 
  many 
  tropical 
  genera, 
  the 
  fleshy 
  

   fruits 
  being 
  eaten 
  by 
  birds 
  and 
  monkeys, 
  and 
  the 
  seed 
  scattered. 
  Vari- 
  

   ations 
  of 
  structure 
  or 
  habits 
  within 
  the 
  species, 
  such 
  as 
  thicker 
  bark 
  

   or 
  greater 
  tolerance 
  of 
  drought 
  or 
  other 
  unfavorable 
  conditions, 
  may 
  

   have 
  cultural 
  importance 
  far 
  beyond 
  the 
  characters 
  formulated 
  in 
  

   describing 
  species 
  in 
  the 
  usual 
  manner, 
  that 
  is, 
  from 
  differences 
  in 
  

   leaves, 
  flowers, 
  or 
  fruits. 
  

  

  