148 
Digitalis  Thapsi  Lin. 
Am.  Jour.  Pharm. 
April,  19 1 7. 
abruptly  expanded  into  a  tube  much  longer  than  the  usually  5-lobed, 
slightly  2-lipped  limb  ;  stamens  4,  didynamous,  attached  low  down  on 
the  tube,  included;  calyx  present,  glandular,  5 -parted,  about  f/5  the 
length  of  the  corolla,  segments  lanceolate.  Capsules  ovoid,  about  15 
Mm.  in  length,  greenish  and  more  or  less  glandular,  to  pale  brownish 
or  yellowish  green,  with  only  traces  of  the  glandular  indument,  with 
fragments  of  the  calyx  at  the  base,  on  a  slender  pedicle,  3  Cm.  or 
less  in  length,  which  is  clavate  under  the  capsule ;  fruit  partially  sep- 
arating into  two,  one-celled,  many-seeded  sections,  opening  at  the 
apex  on  the  inner  surface  by  a  large  pore.  Odor,  slight;  taste, 
bitter  and  slightly  acrid.  This  drug  is  not  the  official  Digitalis  pur- 
purea Lin.  as  the  leaves  are  sessile,  somewhat  decurrent,  and  of  the 
same  color  on  both  sides.  It  may  be  the  closely  related  D.  Thapsi 
Lin.  A  cross-section  of  the  upper  portion  of  a  stem,  2^2  Mm. 
thick,  shows  a  pith  1  Mm.  in  diameter  surrounded  by  a  circle  of 
wood  (Fig.  6,  D),  0.3  Mm.  wide  and  a  bark  about  .5  Mm.  The 
outer  bark  shows  epidermal  cells  that  are  small  (12-20  microns) 
with  rather  thick  outer  walls  covered  with  a  strongly  papillate  cuticle 
(Fig.  7,  A)  ;  immediately  under  the  epidermis  is  a  layer  (130 
microns)  of  unlignified  hypodermal  cells  5-8  tiers  in  depth  (Fig.  7, 
B)  ;  internally  to  this  is  a  layer  of  parenchyma  (Fig.  8),  of  equal 
depth  but  composed  of  fewer,  4-6  tiers  of  cells  ;  the  inner  bark  (Fig. 
6)  is  made  up  of  a  continuous  circle  of  bast  (A)  130  microns  deep 
and  a  narrower  layer  of  sieve  tissue  (B) .  The  cells  of  the  pith  (E) 
often  reach  a  size  of  70  microns  in  diameter,  are  slightly  lignified 
or  cutinized  and  non-porous.  The  stomata  (Fig.  9)  on  the  leaf 
occur  in  the  ratio  of  about  8  to  an  area  of  150  microns  square. 
The  epidermis  is  essentially  the  same  as  for  the  green  bark  of  the 
stem.  The  palisade  tissue  is  one  cell  in  depth;  the  cells  of  the 
sponge  tissue  are  well  filled  with  oil.  No  crystals  were  detected. 
The  midrib  (Fig.  10)  forms  a  very  prominent  keel  on  the  dorsal 
(lower)  surface  of  the  leaf.  The  vascular  strand  is  rather  broadly 
ovate  in  outline,  the  phloem  passing  almost  completely  around  the 
xylem.  On  the  ventral  side  there  are  several  layers  of  collenchyma 
and  on  the  dorsal  side  the  greater  part  of  the  tissue  consists  of  the 
water-storage-cells  with  a  layer  or  two  of  collenchyma  between  it 
and  the  epidermis. 
