AmASt,imm-}      Histology  of  Hyoscyamus  Muticus.  363 
The  epidermis  consists  of  a  row  of  regular  cells  having  a  thick 
cuticle.  (Fig-  1,  Lying  adjacent  to  the  epidermis  is  the  cortex, 
composed  of  large,  thin- walled  cells  which  are  tangentially  stretched. 
(Fig.  1,  c.)  In  a  stem  measuring  7  mm.  in  diameter,  the  cortex  is 
about  15  cells  in  width.  These  cells  measure  radially  from  10 
microns  near  the,  epidermis  to  70  in  the  central  part  of  the  cortex, 
and  tangentially  from  25  to  150.  The  vascular  bundles  are  bicol- 
lateral,  having  small  groups  of  phloem  adjoining  the  medulla  as  well 
Fig.  2. — D,  Longitudinal  section  of  stem  ;  epidermis,  a;  cortex,  k.  E>  Lon- 
gitudinal radial  section  of  xylem  ;  i,  duct,  and  m,  wood  fibers  ;  o,  a  trichome 
from  the  inner  surface  of  the  calyx  ;  p,  trichome  from  stem  ;  r,  longitudinal 
radial  section  of  medullary  ray. 
as  the  larger  groups  adjacent  to  the  cortex.  The  xylem  is  composed 
for  the  most  part  of  wood  fibers  and  ducts.  (Fig.  i,C.)  The  ducts 
are  relatively  few,  and  occur  singly  or  in  groups  of  two  or  three, 
rarely  more,  and  are  annular,  spiral,  scalariform  or  reticulate  in 
structure. 
The  latter  may  contain  either  simple  or  bordered  pores.  The 
xylem  is  rich  in  fibers  which  are  relatively  thick-walled.    (Fig.  1,  i.) 
