AmNJo°vUri^8arin'}    The  Microscope  in  Materia  Medic  a. 
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determining  the  development  of  one  tissue  at  the  expense  of  another  \ 
for  instance,  holly  cultivated  in  a  rich  soil  loses  the  spiny  character  of 
its  leaves  due  to  prosenchymatous  tissue  in  the  excessive  development 
of  its  parenchymatous  tissue.  Some  medicinal  plants  by  garden 
cultivation  lose  much  of  their  medicinal  activity.  Schroff  states  that 
this  is  the  case  with  the  aconites,  and  Hanbury  mentions  that  the 
variation  in  quantity  of  volatile  oil  yielded  by  valerian  is  influenced  by 
locality,  a  dry  and  stony  soil  yielding  a  root  richer  in  oil  than  one  that 
is  moist  and  fertile,  and  I  have  but  little  doubt  that  this  influence  of 
soil  is  accompanied  by  a  corresponding  alteration  in  the  histological 
elements  of  the  valerian  root. 
Facts  such  as  these  are  very  suggestive  to  the  pharmacist,  and  they 
may,  on  a  little  reflection,  be  much  extended  ;  but  they  are  sufficient 
to  show  the  value  of  a  study  of  vegetable  histology,  without  which  the 
influence  of  soil,  climate  and  cultivation  on  the  development  of  par- 
ticular elementary  tissues  cannot  be  accurately  determined. 
A  parcel,  supplied  as  senega  root  in  the  usual  course  of  business  to 
a  pharmacist,  was  forwarded  to  me  for  microscopical  examination.  Its 
being  a  senega  root  at  all  was  called  in  question.  It  will  be  observed 
from  the  sample  that  the  roots  are  thinner,  of  a  lighter  color,  and  have 
fewer  rootlets  than  the  senega  usually  met  with  in  commerce.  Also 
the  dark  concentric  rings  are  not  present,  and  there  is  an  absence  of 
keel,  with  other  characters  of  lesser  importance.  A  decoction  of  it,  as 
compared  with  one.  from  an  ordinary  samplers  much  lighter  in  color  and 
in  taste  much  less  pungent.  The  histological  examination  proved  it  to 
be  a  true  root  of  Polygala  senega;  a  transverse  section  of  it  is  repre- 
sented by  No  i  drawing.  No.  2  is  a  section  of  a  root  of  a  senega  of 
commerce  taken  across  a  keel,  and  showing  the  general  structure  to  be 
similar  to  the  preceding.    No.  3  is  a  section  of  one  of  the  rootlets. 
I  shall  now  proceed  to  describe  the  tissues  histologically.    For  this 
