^""-jXJt""-}  Structure  of  Dye-Woods,  347 
To  any  one  possessing  a  microscope  and  micrometer,  with  some 
skill  in  the  use  of  the  same,  aided  also  by  the  publications  referred  to,, 
the  task  of  distinguishing  the  different  varieties  of  dye-woods  is  easy 
but  to  a  person  having  only  a  lens  difficulties  present  themselves,  the 
removal  of  which,  as  far  as  possible,  is  the  object  of  this  communica- 
tion. I  would  return  thanks  to  the  gentlemen  mentioned  above  for 
the  material  placed  at  my  service.  It  was,  in  every  respect,  all  that 
was  required,  and  also  affords  sufficient  guarantee  for  the  general  valid- 
ity of  the  characteristics  described  below. ^ 
Having  but  a  splinter  of  the  wood,  it  is  easy,  with  the  help  of  a 
a  cross  section,  that  can  be  got  without  trouble,  to  form  accurate  radial 
and  tangential  sections,  as  well  as  to  produce  cleavage  planes,  which 
would  furnish  all  the  cardinal  points  necessary  for  the  carrying  out  of 
the  following  examination. 
A  preliminary  examination  of  the  cross  section  with  the  glass  will 
show  that  dye-woods,  and  woods  most  nearly  related  to  them,  can  be 
arranged  in  a  number  of  groups,  which,  as  regards  their  structure,  are 
sharply  defined  and  separated  from  each  other,  but  within  these  groups 
reliable  distinction  is  attended  with  great  difficulty.  The  groups  are  : 
I.  Blue-wood.  2.  The  inferior  varieties  of  Red-wood  from  America; 
Lima,  Costa  Rica,  Santa  Martha  red-wood  and  others.  3.  Brazil- 
wood, Sapan-wood  and  Coulteria  Red-wood.    4.  Red  Sandal-wood 
^  For  present  information  I  will  remark  that  the  entire  wood  portion  of  the  dye- 
woods,  as  regarded  for  present  purposes,  consists  of  parenchyma,  wood  fibre,  medul-. 
lary  rays  and  ducts.  The  rays  appear  on  the  cross  section,  often  to  the  naked  eye,, 
but  always  under  a  lens  of  4  to  5  magnifying  power,  as  delicate,  pale,  parallel  lines, 
which  are  usually  embedded  in  a  darker,  solid  background,  consisting  of  wood- 
fibre.  The  direction  of  the  medullary  rays  is  the  radial.  A  section  in  this  line  is 
called  the  radial  section.  Perpendicular  to  the  radial  line  (tangential)  show  on  the 
cross  section  other  fine  and  somewhat  wavy  lines,  which  represent  the  limits  of  the 
annual  rays.  The  longitudinal  section,  perpendicular  to  the  radial  section,  is  called 
the  tangential  section.  It  intersects  all  the  medullary  rays  obliquely,  while  the 
radial  section  lays  them  bare  throughout  its  length.  The  wood  fibres  and  ducts 
appear  on  the  cross  section  as  cut  perpendicularly.  The  first  form,  to  a  certain 
extent,  the  background  of  the  wood.  They  determine  the  hardness  of  the  wood 
body,  and  in  the  cross  section  appear  as  dark,  hard,  closed  masses  of  tissue,  ini 
which  the  masses  of  pale  parenchyma  are  embedded  as  patches  of  round  or 
obliquely  stretched  shape,  or  as  adherent,  narrow  tangential  bands  or  lines.  In  the 
masses  of  parenchyma,  mostly  characterized  by  peculiar  arrangement,  are  the  ducts, 
and  hollow  tubes  disposed  lengthwise  on  the  wood. 
