﻿NATURAL 
  RUBBER 
  — 
  COOK 
  383 
  

  

  determine 
  the 
  presence 
  of 
  rubber. 
  With 
  rubber 
  viewed 
  as 
  a 
  waste 
  

   product, 
  it 
  might 
  be 
  formed 
  in 
  any 
  group 
  of 
  plants, 
  and 
  indeed 
  is 
  

   found 
  in 
  many 
  plants 
  that 
  have 
  no 
  specialized 
  latex 
  system 
  or 
  other 
  

   indication 
  of 
  rubber. 
  The 
  Eucommia 
  tree 
  of 
  China, 
  though 
  not 
  pro- 
  

   vided 
  with 
  latex, 
  has 
  the 
  rubber 
  material 
  sufficiently 
  segregated 
  to 
  show 
  

   many 
  fine 
  elastic 
  threads 
  when 
  the 
  leaves 
  or 
  the 
  bark 
  are 
  broken 
  and 
  

   pulled 
  apart. 
  The 
  guayule 
  shrub 
  is 
  the 
  typical 
  example 
  of 
  a 
  rubber 
  

   producer 
  with 
  no 
  latex 
  or 
  other 
  external 
  sign, 
  the 
  presence 
  of 
  the 
  gum 
  

   being 
  learned 
  from 
  the 
  Indians 
  who 
  obtained 
  it 
  by 
  chewing 
  the 
  bark. 
  

  

  The 
  tendency 
  to 
  think 
  of 
  rubber 
  only 
  in 
  terms 
  of 
  latex 
  plants 
  still 
  

   is 
  dominant. 
  The 
  only 
  investigator 
  to 
  face 
  the 
  question 
  of 
  finding 
  

   rubber 
  among 
  the 
  plants 
  without 
  latex 
  was 
  the 
  great 
  inventor, 
  Thomas 
  

   A. 
  Edison, 
  who 
  was 
  inclined 
  to 
  believe 
  that 
  the 
  storehouse 
  of 
  nature, 
  

   if 
  sufficiently 
  searched, 
  would 
  meet 
  any 
  special 
  requirements. 
  In 
  the 
  

   hope 
  of 
  finding 
  rubber 
  in 
  a 
  plant 
  that 
  could 
  be 
  grown 
  in 
  the 
  United 
  

   States, 
  preferably 
  as 
  a 
  field 
  crop, 
  large 
  numbers 
  of 
  weeds 
  and 
  other 
  

   common 
  plants 
  were 
  assayed 
  for 
  rubber, 
  leading 
  to 
  the 
  discovery 
  of 
  

   rubber 
  among 
  the 
  goldenrods. 
  Many 
  members 
  of 
  this 
  group 
  were 
  

   subjected 
  to 
  intensive 
  study 
  and 
  selection, 
  to 
  find 
  a 
  type 
  of 
  plant 
  

   adapted 
  to 
  general 
  cultivation. 
  Because 
  they 
  were 
  so 
  common 
  and 
  

   so 
  widely 
  distributed 
  in 
  the 
  United 
  States, 
  the 
  goldenrods 
  appeared 
  

   promising, 
  but 
  cultural 
  limitations 
  were 
  encountered. 
  The 
  rubber 
  

   is 
  formed 
  mostly 
  in 
  the 
  leaves, 
  and 
  these 
  are 
  difficult 
  to 
  harvest, 
  many 
  

   falling 
  off 
  before 
  the 
  plants 
  mature. 
  

  

  While 
  the 
  goldenrods 
  were 
  being 
  investigated, 
  thousands 
  of 
  other 
  

   plants, 
  mostly 
  natives 
  of 
  our 
  southern 
  States 
  or 
  of 
  adjacent 
  districts 
  

   of 
  Mexico, 
  were 
  examined, 
  and 
  rubber 
  was 
  found, 
  at 
  least 
  in 
  small 
  

   traces, 
  in 
  hundreds 
  of 
  species 
  where 
  none 
  had 
  been 
  known. 
  Some 
  of 
  

   the 
  plants 
  were 
  propagated 
  for 
  preliminary 
  tests, 
  but 
  the 
  goldenrods 
  

   remained 
  the 
  chief 
  interest. 
  Records 
  of 
  Edison's 
  work 
  were 
  placed 
  

   with 
  the 
  United 
  States 
  Department 
  of 
  Agriculture, 
  and 
  the 
  rubber 
  

   assays 
  were 
  continued 
  on 
  many 
  other 
  plants. 
  Such 
  assays 
  no 
  doubt 
  

   are 
  being 
  made 
  in 
  many 
  other 
  countries 
  in 
  view 
  of 
  the 
  present 
  scarcity 
  

   of 
  rubber. 
  An 
  eventual 
  completion 
  of 
  the 
  Edison 
  project 
  may 
  be 
  

   hoped 
  for 
  — 
  a 
  world-wide 
  extension 
  of 
  the 
  survey 
  he 
  undertook. 
  Edi- 
  

   son, 
  like 
  La 
  Condamine, 
  contributed 
  a 
  new 
  element 
  of 
  interest 
  in 
  the 
  

   science 
  of 
  rubber, 
  the 
  project 
  of 
  determining 
  all 
  the 
  potential 
  sources 
  

   of 
  production. 
  

  

  Although 
  Edison's 
  search 
  was 
  projected 
  for 
  herbs 
  or 
  shrubs 
  to 
  be 
  

   used 
  for 
  field 
  crops, 
  it 
  should, 
  of 
  course, 
  extend 
  to 
  trees 
  — 
  not 
  only 
  to 
  

   those 
  of 
  temperate 
  regions, 
  but 
  to 
  the 
  tropical 
  trees 
  as 
  well. 
  Rubber 
  

   trees 
  or 
  lianas 
  without 
  latex 
  are 
  as 
  likely 
  as 
  shrubs 
  or 
  herbs. 
  Eucom- 
  

   mia 
  is 
  an 
  example 
  of 
  such 
  a 
  tree. 
  Even 
  if 
  important 
  rubber 
  discoveries 
  

   were 
  not 
  made, 
  such 
  a 
  survey 
  could 
  be 
  expected 
  to 
  yield 
  valuable 
  ex- 
  

  

  