526 
Analysis  of  Vegetable  Tissues. 
f  Am.  Jour.  Pharm. 
X       Oct.,  1883. 
(6)  Paracellulose. — Dissolves  in  the  copper  reagent  only  after  the  addition 
of  an  acid.  This  constitutes  the  utricular  tissue  of  certain  roots,  and  the 
epidermal  cells  of  leaves. 
(c)  Metacellulose. — Insoluble  in  the  copjoer  reagent  even  after  the  addition 
of  acids.  It  occurs  principally  in  the  tissue  of  Fungi  and  lichens,  and  is  the 
"  fungine"  of  Braconnot. 
2.  Vasculose. — This  is  the  substance  which  enters  most  largely  into  the 
composition  of  vessels  and  tracheids.  It  usually  accompanies  cellulose 
substances,  but  differs  from  them  completely  in  composition  and  properties, 
containing  more  carbon  and  less  hydrogen.  It  is  the  substance  which  in 
certain  cases  unites  the  cells  and  the  fibers.  It  sometimes  occurs  on  the 
exterior  of  tissues  in  the  form  of  a  continuous,  resisting  and  horny  mem- 
brane. It  forms,  in  fact,  the  solid  part  of  woody  tissues  ;  it  is  abundant  in 
hard  woods,  and  in  the  sclerenchymatous  concretions  in  pears ;  the  shells 
of  nuts  and  the  stones  of  stone-fruit  often  consist  of  this  substance  to  more 
than  half  of  their  weight.  Vasculose  is  insoluble  in  bi-hydrated  sulphuric 
acid,  and  in  the  coj^per  reagent ;  it  does  not  dissolve  sensibly  at  the  ordinary 
I)ressure  in  alkaline  solvents,  but  only  with  the  assistance  of  pressure.  This 
important  property  is  utilized  in  the  manufacture  of  paper  from  straw  and 
wood.  It  dissolves  rapidly  in  oxidizing  substances,  as  chlorine  water, 
hypochlorites,  nitric  acid,  chromic  acid,  permanganates,  etc.  Before  dis- 
solving it,  oxidizers  change  it  into  a  resinous  acid,  soluble  in  alkalies. 
Cellulose  substances  can  be  removed  from  vasculose  by  the  solvent  action 
on  them  of  bi-Jiydrated  sulphuric  acid,  or  Schweitzer's  reagent.  If,  on  the 
other  hand,  these  substances  have  to  be  freed  from  vasculose,  the  tissue  is 
subjected  for  several  hours  to  the  action  of  nitric  acid  diluted  with  its  volume 
of  water  in  the  cold,  which  does  not  act  sensibly  on  cellulose  substances, 
while  it  transforms  the  vasculose  into  a  yellow  resinous  acid,  which  can 
then  be  dissolved  out  by  means  of  an  alkali. 
3  Cutose. — This  substance  constitutes  the  fine  transparent  membrane 
which  forms  the  surface  of  the  aerial  parts  of  plants;  the  " suberine "  of 
Chevreul  is  a  compound  of  cutose  and  vasculose.  It  possesses  several  char- 
acters in  common  with  vasculose,  resisting  the  action  of  bi-hydrated  sul- 
phuric acid,  but  it  is  soluble  at  the  ordinary  pressure  in  dilute  or  carbonated 
solutions  of  potassa  and  soda.  It  contains  more  carbon  and  hydrogen  than 
vasculose.  Subjected  to  the  action  of  nitric  acid  it  gives  rise  to  suberic  acid. 
To  separate  cutose  from  the  cellulose  substances,  and  from  vasculose,  the 
copper  reagent  is  first  used  to  dissolve  the  former,  and  the  tissue  is  then 
agitated  with  potassa  at  the  ordinary  or  at  a  higher  pressure,  the  former 
dissolving  the  cutose,  and  the  latter  the  vasculose. 
4.  Pectose. — This  substance  is  insoluble  in  water,  but  is  dissolved  by  the 
action  of  dilute  acids,  and  converted  into  pectin.  It  occurs  ordinarily  in 
the  utricular  tissues  of  roots  and  fruits,  and  is  recognized  by  subjecting  the 
tissue  with  heat  to  the  action  of  dilute  hydrochloric  acid  ;  it  then  forms 
pectin,  which  dissolves  in  the  water,  and  can  be  precipitated  by  alcohol. 
5.  Calcium  pectate. — This  salt  is  often  the  basis  of  a  tissue  which  occurs 
in  the  form  of  a  continuous  membrane,  serving  as  in  the  pith  of  certain 
trees  to  bind  the  cells  together.    If  this  salt  is  decomposed  by  an  acid,  the 
