348 
Structure  of  Dye-Woods, 
Am.  Jour.  Pharm. 
July,  1880. 
(African  and  Indian).  5.  Cam-wood.  6.  Madura  Yellow-wood. 
7.  Barberry-wood.     8.  Rhus  Cotinus  Yellow-wood  (Fustic). 
All  these  groups  can  be  distinguished  from  each  other  without  the 
use  of  the  microscope.  The  blue-wood  (Campeachy),  however,  is  not 
always  easily  distinguished  from  some  of  the  inferior  varieties  of  red- 
wood by  studying  its  structure  by  the  aid  of  the  lens.  I  give  below 
accurately  described  characteristics  of  the  several  groups,  with  particu- 
lar reference  to  distinguishing  properties  of  the  individual  woods.  The 
accompanying  figures  are  sections  as  seen  with  a  lens. 
I.  Blue-wood. — The  medullary  rays  are  partly  visible  to  the  naked 
eye.  There  is  also  a  dark  brown  background,  approaching  black  in 
color,  in  which  lie  faint  red  lines,  points  and  streaks.  The  cross  sec- 
tions of  the  ducts  are  not  generally  noticeable  as  such.  In  other  cases 
(varieties  in  Domingo  blue-wood)  the  pale  parenchymous  tissue  predomi- 
nates, and  eventually  forms  the  base  in  which  the  wood  tissue  (fibre) 
is  lodged,  in  the  form  of  small  patches.  In  such  cases  the  ducts  are 
always  somewhat  wider  and  plainly  visible  as  hollow  tubes  (to  o  25 
mm.  width). 
Upon  the  tangential  and  radial  sections  the  ducts  can  yet  be  plainly 
recognized  as  half  tubes.  (With  Brazil-wood  this  is  not  the  case.) 
The  medullary  rays  are  not  visible  on  the  tangential  section.  They 
appear  radially  as  cross  bands  of  very  different  widths,  and  clear  and 
brilliant.  The  broadest  medullary  rays  vary  from  2  to  3  mm.  in  width; 
between  them  are  visible  delicate  cross  lines,  corresponding  to  the 
small  rays  and  never  so  regularly  arranged  as  in  Brazil-wood. 
The  lens  discloses  on  the  cross  section  a  tissue  arrangement  as  seen 
in  Figs.  I  and  2.  The  clear  but  dull  parenchyma  is  (as  in  all  the  fig- 
ures) dark,  and  the  medullary  rays  appear  perpendicular.  They  never, 
as  a  rule,  form  exactly  straight  lines,  and  are  characteristically  of  dif- 
ferent thickness.  When  the  parenchyma  predominates,  there  the  rays 
as  well  as  ducts  are  more  frequent  and  wider,  and  the  latter  are  dis- 
/posed  in  radial  series. 
The  medullary  rays  very  rarely  occur  tangentially,  and  under  the 
lens  nothing  further  of  any  importance  is  shown  by  either  a  tangential 
or  radial  view. 
