288 
Mucilage  in  Plants. 
A.m.  Jour.  Pharm. 
June,  1898. 
GLYCERIN  METHYLENE  BLUE  SOLUTION. 
Methylene  blue  
Alcohol  (95  per  cent.)  .  .  . 
Glycerin  (nearly  anhydrous) 
0*400  grammes. 
20*  C.C. 
80  *  C.C. 
The  cover-glass  is  put  upon  the  section,  and  in  a  short  time  the 
mucilage  cells  are  stained  blue  (as  Figs.  1,  2,  3)  and  are  readily  dis- 
tinguished from  the  remaining  unstained  cells.  Preparations  so  pre- 
pared may  be  kept  indefinitely.  In  fact  in  a  few  weeks  the  contrast 
is  even  more  marked  than  on  the  first  day. 
The  nature  of  the  contents  of  the  sub-epidermal  mucilage  cells 
may  be  best  studied  by  sectioning  alcoholic  material  and  mounting 
in  alcohol.  If  to  a  preparation  of  this  kind  an  alcoholic  solution  of 
iodine  is  added,  the  protoplasm  nucleus  and  plastids  become  light 
brown  in  solor.  If  to  a  transverse  section  in  alcohol  (as  Fig.  4.)  is 
added  chlorzinciodide,  the  mucilage  gradually  swells,  and  the  sub- 
epidermal cell  becomes  about  twice  the  size  as  when  seen  in  alcohol. 
The  wall  between  the  two  cells  becomes  blue,  but  the  mucilage  is  not 
altered  in  cdlor.1  Surface  sections  of  the  leaf,  treated  with  an  alco- 
holic iodine  solution,  and  then  with  an  alcoholic  sulphuric  acid  solu- 
tion (containing  two  volumes  of  alcohol  to  one  volume  of  concen- 
trated H2S04),  allow  for  a  closer  study  of  the  nature  of  the  contents. 
{Fig.  5)  The  nucleus  is  central  and  is  surrounded  by  a  small  amount 
of  cytoplasm.  From  here  to  the  peripherical  layer  of  the  protoplasm 
extend  numerous  threads  of  the  same  substance.  In  the  periphery 
are  a  number  of  small  plastids,  being  fewer  and  smaller  than  in  the 
epidermal  cells. 
The  fresh  pulp  of  banana  fruit  treated  with  an  alcoholic  methy- 
lene blue  solution,  and  from  which  sections  are  made  and  examined 
in  a  glycerin  methylene  blue  solution,  indicate  that  along  the  phloem 
portion  of  each  of  the  fibro-vascular  bundles  we  have  a  chain  of 
cells  (four  to  six  times  larger  than  the  starch-containing  parenchyma 
cells)  which  contain  a  mucilage.  They  take  on  a  deep  blue  color 
{Fig.  J)  and  occur  only  associated  with  the  fibro-vascular  bundles. 
Their  position  and  arrangement  lead  to  the  opinion  that  they  are  in 
the  nature  of  membered  mucilage  tubes  similar  to  the  tannin  tubes 
of  the  oaks. 
1  For  behavior  of  mucilages  toward  iodine  compounds  and  other  reagents, 
see  Arthur  Meyer, Wissenschaftliche  Drogenkunde,  S.  47  and  Tschirch,  loc.  cit.t 
S.  206. 
