﻿384 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  194 
  3 
  

  

  perience 
  and 
  information, 
  for, 
  doubtless, 
  many 
  other 
  materials 
  as 
  im- 
  

   portant 
  as 
  rubber 
  remain 
  to 
  be 
  discovered. 
  

  

  RUBBER-FORMING 
  CELLS 
  IN 
  CASTILLA 
  LATEX 
  

  

  Much 
  has 
  been 
  written 
  about 
  rubber 
  latex 
  as 
  a 
  chemically 
  balanced 
  

   emulsion 
  or 
  suspension 
  of 
  small 
  particles 
  of 
  rubber, 
  without 
  consider- 
  

   ing 
  biological 
  facts 
  discovered 
  at 
  the 
  beginning 
  of 
  the 
  present 
  century. 
  

   The 
  bulletin 
  on 
  Castilla 
  rubber 
  published 
  in 
  1903, 
  in 
  a 
  chapter 
  en- 
  

   titled 
  "The 
  Structure 
  of 
  Latex," 
  referred 
  to 
  a 
  paper 
  by 
  Molisch 
  de- 
  

   scribing 
  a 
  rubber 
  globule 
  as 
  surrounded 
  by 
  a 
  thin 
  coating 
  of 
  proto- 
  

   plasm, 
  with 
  a 
  small 
  nucleus 
  on 
  one 
  side. 
  This 
  observation 
  was 
  con- 
  

   firmed 
  in 
  a 
  study 
  of 
  fresh 
  Castilla 
  latex 
  in 
  eastern 
  Guatemala 
  in 
  June 
  

   1907. 
  The 
  globule 
  of 
  rubber 
  material 
  is 
  clearly 
  distinct 
  from 
  the 
  

   protoplasmic 
  envelope, 
  which 
  often 
  shows 
  in 
  profile 
  a 
  somewhat 
  thick- 
  

   ened 
  area, 
  interpreted 
  as 
  a 
  nucleus, 
  of 
  a 
  standard 
  width 
  and 
  thickness, 
  

   but 
  with 
  the 
  peripheral 
  margin 
  somewhat 
  uneven. 
  The 
  globules 
  of 
  

   the 
  fresh 
  latex 
  are 
  in 
  rapid 
  Brownian 
  movement, 
  but 
  gradually 
  come 
  

   to 
  rest, 
  when 
  it 
  can 
  be 
  seen 
  that 
  the 
  peripheries 
  of 
  contiguous 
  globules 
  

   are 
  not 
  at 
  first 
  in 
  optical 
  contact, 
  although 
  the 
  thin 
  separating 
  layer 
  

   eventually 
  disappears, 
  so 
  that 
  the 
  circles 
  of 
  rubber 
  appear 
  to 
  fuse 
  

   where 
  contacts 
  occur. 
  At 
  the 
  same 
  time 
  the 
  rubber 
  material 
  becomes 
  

   distinctly 
  more 
  transparent 
  than 
  when 
  the 
  latex 
  is 
  in 
  fresh 
  condition. 
  

   An 
  oxidizing 
  process 
  is 
  suggested 
  by 
  the 
  gradual 
  change, 
  showing 
  first 
  

   a 
  narrow 
  hyaline 
  rim 
  around 
  the 
  margin 
  of 
  a 
  cover 
  glass, 
  while 
  the 
  

   central 
  area 
  is 
  still 
  opalescent 
  like 
  the 
  fresh 
  latex. 
  

  

  CASTILLA 
  HANDICAPPED 
  BY 
  AN 
  ENZYME 
  

  

  The 
  presence 
  of 
  a 
  natural 
  ferment 
  or 
  oxidizing 
  enzyme 
  in 
  the 
  Cas- 
  

   tilla 
  tree 
  has 
  complicated 
  several 
  problems 
  of 
  utilization 
  of 
  the 
  rub- 
  

   ber, 
  and 
  of 
  the 
  tree 
  as 
  well. 
  The 
  latex 
  as 
  it 
  oozes 
  from 
  the 
  margins 
  of 
  

   a 
  cut 
  is 
  creamy 
  white, 
  but 
  in 
  a 
  few 
  minutes 
  shows 
  a 
  brownish 
  tinge, 
  

   and 
  drops 
  of 
  watery 
  brownish 
  liquid 
  soon 
  appear 
  to 
  separate 
  from 
  the 
  

   creamy 
  latex 
  and 
  run 
  down 
  the 
  bark 
  of 
  the 
  tree. 
  Some 
  of 
  the 
  creamy 
  

   latex 
  may 
  run 
  down, 
  or 
  all 
  may 
  remain 
  in 
  the 
  cut, 
  to 
  form 
  the 
  "scrap 
  

   rubber," 
  which 
  gradually 
  darkens 
  on 
  the 
  surface 
  to 
  nearly 
  black. 
  The 
  

   shreds 
  or 
  strands 
  of 
  rubber, 
  usually 
  pulled 
  from 
  the 
  cuts 
  in 
  2 
  or 
  3 
  days, 
  

   are 
  white 
  or 
  light 
  color 
  inside, 
  but 
  eventually 
  blacken 
  throughout. 
  

  

  More 
  serious 
  than 
  these 
  color 
  changes 
  is 
  the 
  slow, 
  persistent 
  digestive 
  

   or 
  corrosive 
  action 
  of 
  the 
  enzyme 
  on 
  the 
  rubber. 
  After 
  a 
  few 
  weeks 
  or 
  

   months 
  the 
  surface 
  of 
  a 
  rubber 
  sample 
  becomes 
  soft 
  and 
  sticky, 
  and 
  

   the 
  change 
  continues 
  gradually 
  through 
  months 
  and 
  years, 
  so 
  that 
  

   even 
  a 
  large 
  mass 
  of 
  rubber 
  eventually 
  is 
  reduced 
  to 
  paste. 
  Washing 
  

   the 
  latex 
  was 
  tried 
  in 
  the 
  early 
  years, 
  to 
  prevent 
  discoloration 
  and 
  

   softening 
  of 
  the 
  rubber, 
  but 
  this 
  proved 
  to 
  be 
  entirely 
  ineffective. 
  Such 
  

  

  