334 
A  Species  of  Commelina. 
A.m.  Jour.  Pharm. 
July,  1898. 
the  stem,  leaf  and  bracts.  The  stem  is  more  or  less  but  irregularly 
cylindrical,  somewhat  flattened  upon  one  side.  It  consists  of  the 
usual  epidermis  found  in  plants.  The  stomata,  however,  are  raised. 
Under  the  epidermis  occur  3-6  layers  of  collenchymatic  cells  which 
are  but  to  yt>  the  size  of  the  parenchyma  cells  underlying  these 
layers.  A  well-defined  cylinder  sheath,  composed  of  rather  large 
and  strongly  suberized  and  lignified  cells,  extends  around  the  four- 
teen fibro-vascular  bundles.  Between  the  latter  are  several  layers 
of  lignified  cells.  The  remainder  of  the  stem  towards  the  center 
consists  of  parenchyma,  in  which  are  seventeen  fibro-vascular  bun- 
dles. Many  of  the  large  parenchyma  cells  of  the  pith  contain 
mucilage  which  is  readily  detected  by  the  iodine  or  methylene  blue 
method  recommended  by  Professor  Kraemer  (American  Journal 
of  Pharmacy,  June,  1898).  The  remaining  parenchyma  cells  of  both 
pith  and  cortex  contain  crystals  of  calcium  oxalate  (Fig.  8)  and 
starch  (Fig.  g).  It  may  be  worthy  of  mention  that  a  movement  of 
protoplasm  was  very  perceptible  in  some  of  the  parenchyma  cells 
upon  making  a  longitudinal  section  of  the  fresh  stem. 
The  fibro-vascular  bundles  are  of  the  collateral  type  characteristic 
of  monocotyledons.  The  ducts  vary  in  number  from  two  to  four> 
and  are  either  annular  or  spiral.  The  nature  of  the  cells  of  the  cylin- 
der sheath  and  mucilage  cells  were  not  studied  to  the  extent  that 
they  warrant.  The  character  of  the  substance  on  the  external  and 
internal  walls  and  side  walls  of  the  cells  of  the  cylinder  sheath  are 
peculiar,  and  differ  from  each  other  apparently.  The  mucilage  has 
much  the  appearance  as  though  it  were  in  the  nature  of  a  cell-con- 
tent mucilage.  In  longitudinal  section  the  mucilage  cells  lie  very 
near  the  fibro-vascular  bundles  of  the  pith  and  in  juxtaposition  to 
each  other  in  longitudinal  rows. 
Transverse  sections  of  the  leaf  show  rather  large  epidermal  cells. 
The  walls  of  these  epidermal  cells  are  very  thick.  The  stomata 
appear  to  be  confined  wholly  to  the  lower  surface.  The  guard  cells, 
i<  Nebenzellen,"  and  another  row  of  cells  are  decidedly  raised  above  the 
remaining  epidermal  cells.  The  respiratory  cavity  is  rather  large. 
The  tissue  between  the  upper  and  lower  epidermis  consists  of  palisade 
and  loose  parenchyma  cells.  The  palisade  cells  are  rather  short  and 
somewhat  loosely  arranged,  and  are  made  up  of  a  single  row  of  cells. 
The  loose  parenchyma  cells  are  about  three  rows  in  number  and 
the  walls  are  much  thinner  than  the  palisade  cells. 
