302  Alexandria  and  India  Senna.  {^I^lxm^' 
the  Alexandria  senna,  the  average  size  of  the  cells  of  the  India 
senna  may  be  somewhat  greater  than  those  of  the  Alexandria 
senna.  Likewise,  the  cell  walls  alone  will  not  serve  as  a  point  of 
differentiation,  owing  to  the  same  lack  of  uniformity.  As  regards 
the  shape  of  the  cells,  no  distinctive  value  whatever  can  be  placed 
upon  it,  owing  to  the  great  variability  present.  The  same  may  also 
be  said  concerning  the  arrangement  of  cells  around  the  hairs.  The 
Fig.  3.  Alexandria  senna,  under  side  of  leaf ;  a,  epidermal  cell  ;  b,  stomata  ; 
c,  hair  (scarcely  in  focus)  ;  d,  hair  scar  ;  e,  nebenzellen. 
distinction  here  made  by  Schneider  does  not  hold,  as  a  rule,  although 
a  small  majority  of  cases  may  be  found  to  accord  with  the  state- 
ments made  by  this  authority.1 
In  thirty  cases,  the  stomata  of  Alexandria  senna  showed  sixteen 
with  two  neighbor-cells  (nebenzellen)  and  fourteen  with  three. 
Forty  stomata  on  the  epidermis  of  India  senna  exhibited  twenty- 
1  American  Druggist,  April  10,  1897,  p.  195. 
