38 
ON  VEGETABLE  MUCILAGE. 
It  is,  therefore,  manifest  that  the  denomination  of  cellulose  has 
hitherto  been  applied,  upon  the  authority  of  Payen,  to  two  classes 
of  substances,  one  of  which  is  colored  blue  by  iodine,  the  other 
brown.  The  blue  color  indicates  the  presence  of  starch,  or  rather 
of  the  substance  out  of  which  starch  is  formed,  and  the  brownish- 
yellow  color  reminds  us  of  inulin.  We  may,  therefore,  divide  the 
mucilaginous  and  cellular  substances  into  two  groups,  the  one  the 
amylon  or  starch-group,  the  other  the  inulin-gronp.  That  inulin 
is  more  allied  to  tragacanthin  or  bassorin  and  arabin  than  to  starch, 
is  shown  by  the  fact,  that,  like  arabin,  \t  rotates  to  the  left  the 
plane  of  polarized  light.  In  common  with  all  the  substances  al- 
lied to  starch,  cellulose,  and  gum,  it  is  changed  into  dextrin  and 
sugar  by  the  action  of  acids. 
Group  the  first  includes  1,  starch  ;  2,  starch-cellulose. 
Group  the  second  includes,  1,  inulin  ;  2,  inulin-cellulose  or  bas- 
sorin. 
The  author  applies  the  name  of  amyl  to  the  starchy,  or  amyla- 
ceous matter,  in  order  to  distinguish  it  from  amylum  or  starch. 
Its  formula  is  C]2  Hl0  Ol0,  and  its  reaction  with  tincture  of  iodine 
characterizes  it.  As,  according  to  Mitscherlich,  starch  cellulose 
consists  of  C12  H,0  O10,  the  whole  difference  between  amyl  and 
starch-cellulose,  denominated  by  the  author,  gelin,  is,  that  the 
amyl  substances  are  instantaneously  colored  blue  by  tincture  of  io- 
dine, and  the  gelin-substances  only  upon  the  additional  influence 
of  sulphuric  acid  (or  of  alkalies.) 
So  also  with  regard  to  the  second  group  :  the  inulin-globules 
are  at  once  colored  orange  or  brownish-yellow  by  iodine,  whereas 
the  bassorin  substances  become  colored  only  upon  the  additional 
application  of  sulphuric  acid.  The  lichen-cells  in  the  cortical 
layer  and  in  the  fruit-parts  of  Cetraria  islandica  consist  of  true 
amyl. 
In  investigating  the  formation  of  gum,  the  author  perceived,  on 
breaking  off  the  exudation  from  a  plum,  that  not  only  the  epider- 
mis, but  also  the  cells  of  the  juicy  parenchyma  wTere  at  this  spot 
in  part  already  decomposed,  and  in  part  undergoing  decomposition; 
the  result  of  which  is,  that  unlike  those  kinds  of  putrefactions, 
which  are  connected  with  the  formation  of  certain  fungi  (Faden- 
pilze,  Strubpilze,  &c.)  the  organic  product  is  a  peculiar,  hitherto 
unknown  fungus,  the  gum-fungus,  or  the  gum  itself.    The  brown 
