ON  CELLULOSE  AND  THE  COMPOSITION  OF  WOOD.  71 
many  other  substances,  it  exerted  no  action  upon  the  cel- 
lular membranes  of  several  algae,  champignons,  the  pith  of  trees, 
cork,  &c. 
M.  Payen,  in  a  paper  on  the  analogies  and  points  of  distinc- 
tion between  cellulose  and  starch,  accounted  for  this  difference 
by  attributing  it  to  the  protecting  action  of  the  intercellular 
matter,  the  incrustations  of  mineral,  fatty,  and  nitrogenous  sub- 
stances, and  the  presence  of  the  epidermis.  He  found,  if  all 
these  foreign  substances  were  removed,  and  the  cellulose  left  in 
a  state  of  purity,  it  was  immediately  dissolved  ;  and  that  when 
again  precipitated  by  acids,  it  had  all  the  properties  and  the 
composition  of  ordinary  cellulose. 
M.  Fremy,  in  a  paper  on  the  composition  of  vegetable  cells, 
showed,  by  means  of  the  new  reagent,  that  the  inner  walls  of 
the  cells  of  fruits,  &c,  consist,  not  of  cellulose,  but  of  a  substance 
which  he  named  Pectose,  and  which,  under  comparatively  slight 
influences,  and  during  the  ripening  of  the  fruit,  is  rendered  sol- 
uble and  converted  into  Pectine.  In  the  course  of  this  paper 
M.  Fremy  expressed  an  opinion  that  cellulose  exists  in  several 
isomeric  conditions,  in  one  of  which  it  is  soluble  in  cuprate  of 
ammonia,  while  in  the  other  it  is  insoluble.  This  view,  opposed 
to  M.  Payen's,  was  more  fully  developed  in  a  subsequent  com- 
munication, entitled  "Distinctive  Characters  of  Ligneous  Fibres, 
Cortical  Fibres,  and  the  Cellular  Tissue  which  constitutes  the 
Pith  of  Trees."  Up  to  that  time  the  utricular  tissues  and  vege- 
table fibres  were  considered  to  be  formed  essentially  of  the  same 
substance,  cellulose.  M.  Fremy  argued,  while  the  cupro-ammo- 
niacal  reagent  immediately  dissolves  the  cortical  fibres  of  all 
plants  and  the  utricular  tissues  of  fruits,  but  exerts  no  action 
upon  the  pith  of  trees,  it  is  difficult  to  consider  these  tissues  as 
being  formed  of  the  same  substance — the  difference  cannot  be  at- 
tributed to  unequal  penetration  by  the  reagent,  because  the  pith 
is  much  more  porous  than  the  mass  of  cortical  fibres  ;  the  impu- 
rity of  the  insoluble  body  cannot  explain  the  difference  in  action 
either,  because  the  pith,  properly  selected,  presents  all  the  char- 
acters of  a  pure  immediate  principle,  containing  but  inapprecia- 
ble quantities  of  mineral  substances.  These  chemical  characters, 
therefore,  establish  a  striking  difference  between  the  cellular  tis- 
sue of  pith  and  cortical  fibres.    The  wood  or  fibrous  tissues  is 
