﻿NATURAL 
  RUBBER 
  — 
  COOK 
  405 
  

  

  gum 
  is 
  like 
  gutta-percha 
  in 
  being 
  tough 
  rather 
  than 
  elastic; 
  it 
  is 
  not 
  

   at 
  all 
  pasty 
  or 
  sticky, 
  as 
  are 
  many 
  of 
  the 
  near-rubbers. 
  

  

  A 
  peculiar 
  feature 
  of 
  the 
  Eueommia 
  gum 
  is 
  that 
  it 
  does 
  not 
  become 
  

   plastic 
  or 
  adhesive 
  when 
  heat 
  up 
  to 
  the 
  boiling 
  point 
  of 
  water 
  is 
  

   applied. 
  Though 
  such 
  a 
  property 
  of 
  resistance 
  to 
  heat 
  is 
  of 
  special 
  

   value 
  in 
  some 
  of 
  the 
  uses 
  of 
  rubber, 
  the 
  lack 
  of 
  cohesion 
  among 
  the 
  

   rubber 
  particles 
  has 
  prevented 
  the 
  application 
  to 
  Eueommia 
  of 
  the 
  

   processes 
  of 
  mechanical 
  extraction 
  that 
  have 
  been 
  developed 
  for 
  

   guayule. 
  Extraction 
  with 
  solvents 
  is 
  possible, 
  and 
  samples 
  obtained 
  

   in 
  this 
  manner 
  leave 
  no 
  doubt 
  that 
  the 
  material 
  is 
  firm, 
  tough, 
  and 
  

   flexible, 
  but 
  costs 
  may 
  be 
  prohibitive 
  unless 
  special 
  uses 
  are 
  discovered. 
  

  

  EUCOMMIA, 
  A 
  TREE 
  THAT 
  NEVER 
  BLOSSOMS 
  

  

  The 
  Eueommia 
  tree 
  has 
  features 
  of 
  such 
  botanical 
  interest 
  as 
  to 
  

   be 
  valuable 
  for 
  purposes 
  of 
  instruction 
  in 
  any 
  institution 
  where 
  

   botany 
  is 
  taught. 
  All 
  universities 
  or 
  other 
  schools 
  that 
  have 
  tree 
  

   collections, 
  or 
  even 
  "garden 
  and 
  grounds," 
  should 
  have 
  Eueommia 
  

   branches 
  as 
  "laboratory 
  material." 
  The 
  period 
  of 
  reproduction 
  is 
  

   in 
  the 
  early 
  spring, 
  when 
  floral 
  botany 
  usually 
  receives 
  attention. 
  

   The 
  tree 
  is 
  vigorous 
  and 
  handsome, 
  the 
  foilage 
  much 
  resembling 
  that 
  

   of 
  an 
  elm, 
  as 
  the 
  specific 
  name 
  indicates. 
  

  

  The 
  educational 
  function 
  that 
  Eueommia 
  may 
  serve 
  most 
  effectively 
  

   is 
  to 
  furnish 
  background 
  for 
  all 
  the 
  courses 
  of 
  study 
  that 
  relate 
  to 
  the 
  

   development 
  of 
  special 
  floral 
  envelopes 
  in 
  the 
  various 
  families 
  of 
  

   higher 
  plants, 
  the 
  "flowering 
  plants," 
  as 
  they 
  are 
  usually 
  called. 
  The 
  

   lack 
  of 
  floral 
  specialization 
  in 
  Eueommia 
  is 
  most 
  complete 
  and 
  re- 
  

   markable; 
  there 
  are 
  no 
  organs 
  that 
  can 
  be 
  interpreted 
  as 
  calyx 
  or 
  

   corolla, 
  or 
  even 
  as 
  a 
  trace 
  or 
  indication 
  that 
  such 
  organs 
  existed 
  pre- 
  

   viously 
  and 
  have 
  been 
  suppressed. 
  A 
  more 
  primitive 
  state 
  or 
  base 
  

   line 
  of 
  floral 
  development 
  is 
  hardly 
  to 
  be 
  imagined. 
  

  

  The 
  stamens 
  and 
  pistils, 
  shown 
  in 
  natural 
  size 
  in 
  plate 
  15, 
  are 
  the 
  

   only 
  floral 
  organs, 
  and 
  these 
  are 
  green 
  like 
  the 
  leaves, 
  so 
  that 
  nothing 
  

   in 
  the 
  nature 
  of 
  a 
  blossom 
  in 
  the 
  popular 
  sense 
  is 
  ever 
  to 
  be 
  seen. 
  An 
  

   alder 
  or 
  a 
  pussy 
  willow 
  has 
  a 
  much 
  more 
  striking 
  "bloom." 
  Not 
  only 
  

   are 
  floral 
  envelopes 
  lacking 
  in 
  Eueommia, 
  but 
  there 
  are 
  no 
  subtending 
  

   bracts 
  or 
  other 
  indications 
  that 
  a 
  specialized 
  inflorescence 
  ever 
  

   existed. 
  The 
  stamens 
  and 
  pistils 
  are 
  mounted 
  directly 
  on 
  simple 
  re- 
  

   ceptacles 
  rising 
  from 
  the 
  axils 
  of 
  the 
  bud 
  scales 
  and 
  the 
  foliage 
  leaves, 
  

   and 
  from 
  the 
  axils 
  of 
  intermediate 
  leaf 
  forms, 
  between 
  the 
  bud 
  scales 
  

   and 
  the 
  foliage 
  leaves. 
  Some 
  of 
  these 
  are 
  slender 
  and 
  weak, 
  not 
  de- 
  

   veloping 
  chlorophyll 
  and 
  soon 
  withering, 
  while 
  others 
  persist 
  through 
  

   the 
  season 
  as 
  undersized 
  leaves. 
  

  

  At 
  Lanham, 
  Md., 
  the 
  buds 
  were 
  noted 
  as 
  completely 
  dormant 
  on 
  

   March 
  9, 
  1936, 
  after 
  protracted 
  cold 
  weather, 
  but 
  as 
  beginning 
  to 
  sep- 
  

  

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