232  How  to  Distinguish  Viburnum  Barks.  {Amj&7;il£?rm* 
from  the  others  is  thus  brought  out  very  visibly.  Taste  much  more 
bitter.    See  Fig.  5. 
Viburnum  Opulus. — A  silvery-gray  powder.  Under  the  micro- 
scope it  presents  a  fibrous  appearance,  the  wood  fibres  being 
numerous. 
In  this  bark  a  solution  of  ferric  chloride  showed  a  decided  reac- 
tion in  bringing  about  a  darkening  of  the  tissues  of  the  middle 
layer.    See  Fig  7. 
As  to  the  drawings  accompanying  this  paper,  I  desire  to  state 
they  represent  the  average  appearance  of  the  powders  represented. 
Several  students  in  the  laboratory  have  verified  the  work,  and  the 
present  illustrations  are  copies  of  the  drawings  of  one  of  our  stu- 
dents— Wm.  V.  Ingham — who  observed  the  directions  I  have  above 
outlined. 
COLORS  OF  POWDERS. 
There  is,  at  present,  no  standard  to  which  shades  of  colors  may 
be  referred.  As  it  is  necessary  to  have  some  standard  for  compari- 
son, and  as  this  work  of  powder  identification  is  in  its  incipiency,  I 
would  suggest  that  a  standard  of  tints  be  recognized  to  avoid  con- 
fusion of  terms.  This  will  appeal  to  any  one  who  has  tried  .to 
identify  powders  or  drugs  from  written  descriptions  of  color.  There 
is,  at  present,  in  existence,  and  accessible  to  every  one,  a  graduated 
standard  of  colors  and  tints  that  would  serve  the  purpose  most  ex- 
actly. I  refer  to  Ridgway's  nomenclature  of  colors.1  Adopting 
this  as  a  standard,  the  colors  of  the  Viburnum  barks  in  No.  60 
powder  would  be  stated  as  follows : 
Viburnum  prunifolium,  trunk  bark  7,  walnut-brown. 
V.  prunifolium,  twig  bark  19,  wood-brown. 
V.  prunifolium,  root  bark  12,  olive-buff. 
V.  opulus  15,  vinaceous-buff. 
This  suggestion  exposes  me  to  the  criticism  of  being  blessed 
with  an  over-refinement  of  nicety,  it  is  true ;  but  the  matter  of 
identification  is  getting  down  to  a  fine  point,  as  it  were,  and  a  sug- 
gestion, such  as  has  been  made,  may  be  at  least  found  worthy  of 
discussion.  It  may  be  argued  that  colors  of  powders  change  from 
many  causes ;  but,  while  this  is  true,  if  a  color  is  mentioned,  it 
should  be  done  in  an  accurate  way. 
1  "A  Nomenclature  of  Colors  for  Naturalists."    By  Robert  Ridgway. 
