Am.  Jour.  Pharm. ) 
Jan  ,1883.  J 
Researches  on  the  Jalaps. 
29 
RESEARCHES  UPON  THE  JALAPS. 
By  a.  Bouriez. 
In  commercial  specimens  of  any  kind  of  true  jalap  (tuberous^  fusi- 
form, or  Taaipico)  several  varieties  of  tubercules  can  be  distinguished 
by  their  external  characters.  Those  which  constitute  the  greater  part 
of  the  jalap,  and  which  I  designate  under  the  name  of 'typical  tuber- 
cules/^ always  present  at  one  of  their  extremities  (the  upper)  the 
remains  of  aerial  organs.  Sometimes  they  .terminate  in  a  point  at  both 
their  extremities ;  sometimes  one  of  the  extremities  only  becomes 
slender,  whilst  the  other  presents  a  large  surface  of  insertion.  There 
iire  met  with,  besides,  tubercules  inserted  on  other  tubercules,  and  very 
small  fragments  [graheaux]  showing  tubercules  inserted  upon  an  organ 
which  is  most  frequently  slender  and  cylindrical,  but  sometimes  fusi- 
form and  more  or  less  swollen.  The  question  presented  itself  to  me, 
whether  these  tubercules  of  the  different  varieties  answered  to  varia- 
tions in  appearance  of  one  and  the  same  organ,  or  whether  they  repre- 
sented organs  of  a  different  morphological  nature. 
An  examination  with  the  naked  eye,  and  aided  by  a  glass,  of  trans- 
verse sections  made  at  different  points  of  these  tubercules,  yielded  me 
some  useful  information,  but  not  sufficient  to  answer  the  question  with 
certainty.  I  then  submitted  the  same  sections  to  a  microscopical 
examination. 
As  a  basis  for  this  micrographic  study  I  selected  a  typical  tuber- 
cule  of  the  tuberous  or  official  jalap. 
A  transverse  section  made  at  the  lower  extremity  of  the  tubercule 
enabled  me  to  conclude  that  the  organ  there  presents  the  structure  of 
a  root.  Towards  the  centre  of  the  section  there  were  observed  four 
primary  woody  layers,  symmetrical  around  the  centre,  and  convergent 
in  pairs.  Each  of  these  layers  is  formed  of  some  spiral  vessels,  the 
most  slender  of  which  are  nearest  the  exterior,  the  largest  being  nearest 
the  centre.  The  differentiation  has  therefore  proceeded  in  each  of 
these  primary  ligneous  layers  from  the  centre  of  development  (indi- 
cated by  the  most  slender  spiral  vessels)  towards  the  centre  of  the 
organ.  It  may  thence  be  concluded  that  the  centre  of  the  organ  is 
occupied  by  a  single  tetracentral  primary  bundle,  the  centre  of  which 
coincides  with  the  centre  of  the  organ,  and  it  may  be  inferred  from 
this  conclusion  that  the  organ,  at  this  stage,  is  a  root. 
•Among  the  histological  details  presented  by  this  root,  I  will  refer 
