Am.  Jour.  Phanii. ) 
May,  1881.  / 
Quebracho  Bark. 
241 
Less  frequently  younger  barks  are  found  with  a  very  moderately 
developed  periderm,  or  the  latter  even  entirely  wanting. 
The  most  striking  peculiarity  in  the  outer  structure  of  the  quebra- 
cho bark  is  the  relatively  exceedingly  strongly  developed  cork, 
which  penetrates  very  deeply  into  the  bark,  often  to  the  extent  of  over 
one-half.  Upon  a  cross-section  of  pieces  of  the  bark  a  boundary  line 
passing  approximately  through  the  middle  of  the  bark  separates  very 
distinctly  the  two  portions  of  tissue,  the  cork  and  the  unchanged  bark 
tissue,  which  are  also  sharply  distinguished  by  their  color  and  internal 
structure.  The  lens  permits  of  recognition  on  a  cross-section  of  the 
cork,  the  outer  surface  of  which  is  grayish,  or  in  scarified  places 
reddish,  a  yellowish-red  fundamental  mass  with  tangentially  penetrat- 
ing serpentine  lines,  diifering  in  color,  and  between  the  same  plainly 
evident  white  points.  The  inner  cortical  layer  consists  for  the  most 
part  of  a  light  brown,  or  occasionally  also  of  a  much  lighter  dirty  yel- 
low tissues,  with  very  numerous  and  irregularly  distributed  whitish 
dots  corresponding  to  those  of  the  cork  tissues. 
While  the  outer  bark,  which  has  been  converted  into  bork,  possesses 
a  somewhat  crumbly  consistence,  the  inner  portion  of  the  bark  con- 
nected with  the  stem  is  hard  and  composed  of  long,  splint-like 
fragments. 
By  a  microscopical  observation  of  the  quebracho  bark  on  a  cross 
section,  the  outer  cortical  tissue  shows  in  a  marked  degree  the  struc- 
tural relations  Avhich  appear  in  the  preponderating  cork.  In  the 
parenchymatous  tissue  with  brown,  often  carmine  colored  cell  walls, 
the  above  indicated  secondary  corky  layers  appear,  consisting  of  uni- 
form rows  of  smaller,  almost  colorless  cells,  and  between  the  same  the 
white  points  or  grains,  which  are  at  once  recognized  as  sclerenchyma, 
or  groups  of  strongly  thickened  cells,  with  a  small  lumen.  A  very 
similar  structure  is  shown  by  the  inner  cortical  layer,  situated  between 
the  bork  and  the  cambium,  although  deviating  somewhat  in  the  col- 
oration of  the  cellular  tissue;  and  here  also  the  groups  of  stone  cells, 
which  microscopically  form  large  white  points,  are  dispersed  in  a 
brown  colored,  often  also  lighter,  parenchymatous  tissue  containing 
starch,  although  the  tangential  cork  bands  are  wanting ;  and  of  the 
radially  extending  medullary  rays,  in  consequence  of  the  irregular 
structure  of  this  tissue  only  a  few  are  plainly  recognizable. 
Among  the  mentioned  sclerenchyma  cells  there  are  many  which  are 
distinguished  from  the  others  by  a  particularly  uniform  circular  out- 
16 
