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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1943 
  

  

  pattern 
  of 
  normal 
  growth 
  has 
  not 
  been 
  lost, 
  but 
  only 
  suppressed 
  during 
  

   the 
  stage 
  of 
  abnormality, 
  as 
  in 
  growth 
  disorders 
  that 
  are 
  caused 
  by 
  

   feeding 
  punctures 
  of 
  plant 
  lice, 
  mealybugs, 
  or 
  leafhoppers, 
  presum- 
  

   ably 
  as 
  effects 
  of 
  salivary 
  secretions 
  of 
  the 
  insects, 
  without 
  virus 
  in- 
  

   fection, 
  so 
  that 
  normal 
  growth 
  is 
  resumed 
  upon 
  removal 
  of 
  the 
  insects. 
  

   Such 
  disorders 
  are 
  known 
  in 
  cotton 
  and 
  many 
  other 
  plants, 
  but 
  these 
  

   malformations 
  are 
  relatively 
  uniform 
  in 
  each 
  disorder, 
  with 
  no 
  such 
  

   individual 
  diversity 
  as 
  in 
  the 
  disordered 
  rubber 
  seedlings. 
  Marked 
  

   diversity 
  with 
  potential 
  recovery 
  is 
  a 
  distinctive 
  feature 
  of 
  the 
  growth 
  

   disorder 
  of 
  the 
  Para 
  rubber 
  seedlings, 
  and 
  the 
  interest 
  of 
  this 
  combi- 
  

   nation 
  is 
  not 
  lessened 
  by 
  ascribing 
  the 
  abnormalities 
  of 
  the 
  rubber 
  

   seedlings 
  to 
  mites 
  or 
  "red 
  spiders," 
  as 
  reported 
  from 
  the 
  Dutch 
  Indies. 
  

  

  A 
  MATURE 
  TREE 
  WITH 
  NARROW 
  LEAVES 
  

  

  That 
  some 
  of 
  the 
  marked 
  variations 
  might 
  survive 
  and 
  reach 
  ma- 
  

   turity 
  is 
  suggested 
  by 
  the 
  discovery 
  of 
  a 
  mature, 
  narrow-leaved 
  tree 
  

   in 
  a 
  neglected 
  planting 
  of 
  Para 
  rubber 
  at 
  Bayeux, 
  Haiti 
  in 
  1925. 
  

   Leaves 
  and 
  flowers 
  of 
  this 
  tree 
  are 
  shown 
  in 
  natural 
  size 
  in 
  plate 
  10, 
  

   in 
  comparison 
  with 
  those 
  of 
  a 
  normal 
  broadleaf 
  tree 
  in 
  the 
  same 
  

   planting. 
  The 
  entire 
  tree 
  was 
  narrow-leaved 
  like 
  the 
  branches 
  that 
  

   were 
  photographed. 
  One 
  branch 
  had 
  a 
  fully 
  developed 
  fruit. 
  Such^ 
  

   an 
  aberrant 
  tree 
  in 
  ordinary 
  practice 
  would 
  be 
  left 
  in 
  a 
  seed 
  bed 
  instead 
  

   of 
  being 
  set 
  in 
  a 
  field 
  planting, 
  but 
  may 
  have 
  grown 
  in 
  this 
  instance 
  

   from 
  a 
  volunteer 
  seedling. 
  Taken 
  by 
  itself 
  such 
  a 
  tree 
  might 
  be 
  re- 
  

   corded 
  as 
  an 
  outstanding 
  mutation, 
  but 
  doubtless 
  should 
  be 
  considered 
  

   against 
  the 
  background 
  of 
  wide 
  diversity 
  appearing 
  as 
  a 
  growth 
  

   disorder. 
  

  

  THE 
  PARA 
  RUBBER 
  TREE 
  AS 
  A 
  HYBRID 
  STOCK 
  

  

  This 
  variability 
  of 
  the 
  cultivated 
  rubber 
  tree 
  may 
  be 
  connected 
  with 
  

   the 
  biological 
  status 
  of 
  the 
  wild 
  stock 
  in 
  South 
  America. 
  Because 
  of 
  

   the 
  geographic 
  position 
  of 
  the 
  species 
  in 
  the 
  lower 
  Amazon 
  valley 
  and 
  

   the 
  adaptation 
  of 
  the 
  seeds 
  for 
  floating, 
  unusual 
  conditions 
  for 
  hybrid- 
  

   ization 
  are 
  afforded, 
  not 
  as 
  a 
  rare 
  contingency, 
  but 
  as 
  a 
  frequent 
  occur- 
  

   rence. 
  Swollen 
  currents 
  from 
  the 
  upper 
  river 
  often 
  reverse 
  the 
  flow 
  

   of 
  the 
  lower 
  tributaries, 
  so 
  that 
  floating 
  seeds 
  may 
  be 
  stranded 
  far 
  

   from 
  the 
  main 
  stream. 
  Thus 
  the 
  stock 
  of 
  Siphonia 
  over 
  a 
  wide 
  area 
  

   of 
  the 
  lower 
  valley 
  must 
  have 
  remained 
  continually 
  accessible 
  to 
  cross- 
  

   ing 
  with 
  the 
  several 
  up-river 
  species. 
  Hybridizing 
  as 
  a 
  preliminary 
  

   to 
  selection 
  has 
  been 
  accomplished 
  in 
  nature. 
  

  

  RUBBER 
  IN 
  A 
  DESERT 
  SHRUB 
  

  

  The 
  third 
  place 
  in 
  rubber 
  history 
  must 
  be 
  accorded 
  to 
  the 
  guayule 
  

   shrub, 
  Parlhenium 
  argentatum, 
  a 
  native 
  of 
  windswept 
  desert 
  table- 
  

  

  