540 
ON  RHATANY  ROOT. 
Verrucarice,  there  was  a  dark-fruited  Lecidea,  "with  a  green 
thallus.  Another  seron  contained  principally  the  roots  and 
stems  of  younger  plants,  which,  at  scarcely  one  inch  above  the 
ground,  had  divided  into  numerous  branches  and  twigs,  the  latter 
clothed  with  a  dense  covering  of  long,  silky,  white,  adpressed 
hairs.  The  foliaceous,  thin,  brittle,  brown  bark,  is  easily  de- 
tached. The  youngest  branches  still  retained  here  and  there 
the  small  oval  leaflets,  invested  with  the  same  covering  of  hairs 
as  the  branches.  According  to  the  testimony  of  travellers,  the 
rhatany  plant  is  easily  recognized,  even  at  a  distance,  not  only 
by  its  bright  red  flowers,  but  also  by  the  silky,  shining  pubes- 
cence of  the  leaves.  Under  the  microscope  this  pubescence  is 
seen  to  consist  of  densely-crowded,  long,  one-celled,  colorless, 
thick-walled,  hollow  hairs. 
According  to  the  age  of  the  plant,  we  find  a  difference  in  the 
external  appearance,  and  more  or  less  in  the  internal  structure, 
of  its  stem — less  so,  however  in  the  roots,  which,  to  us,  are  of 
more  importance. 
The  aerial  stem  of  the  young  plant  is  covered  with  a  reddish- 
brown,  rough,  but  slightly  wrinkled  bark,  which  closely  adheres 
to  the  wood.  A  transverse  section  shows  the  layer  of  bark 
strongly  distinguished  by  its  internal  red  color  from  the  yellowish 
white  wood.  In  older  stems  the  bark  assumes  a  somewhat  dif- 
ferent color  from  a  mixture  of  dirty  brown,  but  the  wood  remains 
the  same.  In  old  stems,  however,  having  cortical  matter  to  the 
thickness  of  a  quarter  of  an  inch,  a  very  different  external  ap- 
pearance is  presented,  such,  in  fact,  as  we  have  noticed  on  the 
trunks  of  old  oaks.  Deep  horizontal  and  perpendicular  fissures 
divide  the  bark  into  a  number  of  irregular  elevated  portions. 
The  perpendicular  fissures  are  broader  and  more  open;  but  less 
deep  than  the  horizontal,  which  sometimes  penetrate  down  to 
the  wood  of  the  tree.  The  connexion  between  wood  and  bark  is 
usually  very  weak  ;  it  therefore  frequently  occurs  that  in  hand- 
ling the  roots  portions  of  the  bark  break  off.  It  often  happens 
that  a  seron  of  180  lbs.  contains  twenty  pounds  of  loose  bark. 
As  the  active  principles  of  the  root-bark  are,  to  some  extent, 
present  in  the  bark  of  the  stem,  it  formerly  occurred  that  the 
[stem-]  bark  was  sold  by  itself  or  mixed  with  root-bark.  Martius 
and  other  writers  on  Materia  Medica  mention  this  ;  it  seems,  how- 
