304 
Alexandria  and  India  Senna. 
Am.  Jour.  Pharru. 
June,  1897. 
stomata  themselves,  a  feature  that  was  overlooked  in  the  prelimi- 
nary paper.  Here  it  will  be  noticed  that  almost  invariably  the 
stomata  of  the  Alexandria  senna  are  smaller  and  much  rounder 
than  those  of  the  India.  References  to  Figs,  i  and  4.  will  make 
this  clear.  Measurements  of  a  considerable  number  of  stomata  in 
each  case  gave  the  following  ratio  between  the  longer  and  shorter 
diameters :  In  Alexandria  the  shorter  diameter  bore  a  ratio  to  the 
larger  of  0-84  to  1  ;  in  the  India,  of  o-6  to  1. 
Occasionally  stomata  of  a  rounded  form  may  be  found  in  the 
India  senna,  but  they  do  not  look  like  the  Alexandria  and  are 
Fig.  5.  Alexandria  senna,  showing  number  of  hairs  in  a  limited  area  ; 
d,  hair  scars  ;  e,  nebenzellen. 
larger.  At  the  present  state  of  the  investigation,  this  character 
represents  by  far  the  most  characteristic  difference  between  the  two 
species  and,  together  with  the  number  of  hairs,  affords  the  best 
means  of  detecting  a  mixture  of  the  two  in  powdered  form. 
The  opinion  reached  by  the  author  in  the  former  paper,  that  the 
number  of  hairs  shown  by  the  two  species  is  a  valuable  means  of 
distinguishing  them  apart,  is,  after  yet  more  careful  research,  again 
advanced.  It  would  seem  at  first  sight  that  the  test  proposed  by 
Schneider,  i.  e.t  estimating  the  number  of  hair  scars  upon  the  epi- 
