Am.  Jour.  Pliarm. ) 
March,  1890.  I 
Collenchymatic  Cork. 
125 
(last)  rows,  viewed  from  above  are  polygonal,  measure  about  0  03 5 
mm.,  and  are  thickened  in  such  a  manner  that  the  tissue  must  be 
designated  as  collenchyma  layer."  This  tissue  is  also  described  as 
collenchyme  by  J.  Moeller  (Mikroskopie  der  Nahrungsmittel,  p.  245) 
who,  however,  states  that  its  membranes  do  not  give  the  reaction 
for  cellulose. 
Having  for  some  time  studied  the  histochemistry  of  capsicum 
fruit,  the  behavior  of  this  tissue  attracted  particular  attention  inas- 
much as,  notwithstanding  the  collenchymatic  character  of  the  cells, 
all  reagents  for  cellulose  gave  negative  results. 
The  histology  of  the  pericarp  of  capsicum  may  be  briefly  sketched 
as  follows :  A  transverse  section  of  a  large  fruit  shows  first  an 
epidermis  composed  of  thick-walled  cells,  followed  by  the  collen- 
chymatic parenchyma  mentioned  above,  in  about  four  to  seven  tiers, 
the  thickened  cell  walls  of  which  do  not  give  the  cellulose  reaction  ; 
then  follows  a  large-celled  thin-walled  parenchyma  having  a  some- 
what collenchymatic  appearance  and  acquiring  a  fine  violet  color  with 
iodine  zinc  chloride  (Chlorzinkjod).  The  succeeding  layer  is  made 
up  of  very  large,  somewhat  viaduct-like  cells  which  are  completely 
collapsed  in  the  dried  pericarp,  and  are  covered  by  the  inner  derma  ; 
the  latter  being  composed  of  thin-walled  non-lignified  and  of 
isolated  thick-walled  lignified  cells.  Conforming  to  the  great  vari- 
ability of  the  genus,  the  structure  is  subject  to  considerable  variations, 
more  particularly  in  regard  to  the  quantitative  development  of  the 
several  layers ;  for  instance,  the  collenchymatic  tissue  may  be 
reduced  to  a  single  cell-layer,  and  in  the  small-fruited  Cayenne 
pepper  is  even  entirely  wanting. 
The  cell-walls  of  the  "collenchyme"  appear  under  the  micro- 
scope colorless  or  yellowish,  and  by  iodine  zinc  chloride  become 
dark  yellow  or  deep  brown,  the  entire  layer  thus  becoming  sharply 
distinct  from  the  cellulose -parenchyma  beneath.  After  prolonged 
action  of  the  reagent  the  innermost  very  thin  layer  of  the  cell  wall 
is  colored  violet,  while  the  remaining  thickening  layers  retain  the 
brown  color.  The  cell  walls  at  the  border  of  the  thick-walled 
and  thin-walled  cells  have  a  thicker  cellulose  film,  and  in  their 
middle  layers  enclose  small  granules  (suberin)  which  give  to  the 
cell  wall  a  granular  appearance.  Treatment  with  iodine  and  sul- 
phuric acid  does,  likewise,  not  result  in  blue  coloration. 
These  cell-walls  are  also  entirely  destitute  of  lignification,  since 
