Amju°yfi£8.arm*}    Coloring  Matter  in  Some  BorraginacecE.  347 
These  facts  prompted  me  to  further  investigate  the  matter.  I 
examined  the  other  specimens  of  the  same  species,  and  others  of 
that  genus  and  related  genera  in  the  Garden  herbarium,  and  found 
that  a  number  of  specimens  had  stained  the  paper  in  the  same  way, 
some  through  as  many  as  five  herbarium  sheets.  The  color  spreads 
through  the  paper  from  the  mounted  plant,  though  in  what  manner 
I  have  not  been  able  to  ascertain. 
It  is  well  known  that  a  coloring  matter  is  common  in  the  roots 
of  several  species  of  Borraginaceae,  and  the  substance  is  probably 
the  same  in  all.  It  is  known  as  alkannin,  and  is  a  non-nitrogenous, 
resinous,  purple  coloring  matter,  soluble  in  oils,  alcohol  and  ether, 
but  not  soluble  in  water.1 
Alkannin,  or  alkanet  (or  alcanet),  as  the  dye  is  called,  is 
obtained  from  the  root  bark  of  Alkanna  tinctoria,  which  is  culti- 
vated in  South  and  Central  Europe,  for  the  dye  which  is  used  in 
pharmacy  for  coloring  salves,  and  for  coloring  wine  and  other 
liquids  sold  as  wine.  Alkanet  is  also  an  excellent  test  for  resins 
and  oils,  to  which  it  gives  a  red  color,  and  is  used  in  micro-chemistry 
as  a  reagent  for  these  substances.  The  dye  is  said  to  give  a  brilliant 
violet  color,  with  iron  and  alum  mordants,  to  linen,  cotton  and  silk, 
but  not  to  wool.  The  fact  that  the  wool,  on  sheep  grazing  among 
growing  plants,  is  colored  is  probably  due  to  the  alkannin  being  dis- 
solved in  the  oil  of  the  wool.  In  the  Old  World  alkannin  occurs 
also  in  quantity  of  commercial  value  in  Arnebia,  Echium,  Symphy- 
tum, Onosma  and  Lithospermum.2 
In  a  brief  examination  I  have  found  but  a  few  references  to  this 
color  in  American  Borraginaceae.  The  color  in  the  roots  of  species 
of  Lithospermum  (the  puccoon  of  the  Indians)  is  well  known ;  and 
Dr.  Gray,  in  the  Synoptical  Flora,  mentioned  one  species  of  Plagio- 
bothrys  (P.  Torreyi),  the  herbage  of  which  "  gives  an  abundant 
violet  stain  to  paper."  It  is  opposed  in  this  character  to  P.  ursinus 
of  similar  habit,  but  "  imparting  no  violet  stain  to  paper."  P.  tinc- 
torius  (Ruiz  &  Pavon),  Gray,  Proc.  Am.  Acad.,  20,  283,  of  South 
America,  is  also  described  as  "  papyros  violaceo  colore  tingens." 
An  examination  of  the  herbarium  material  of  the  Garden  shows 
1  The  information  regarding  the  properties  and  uses  of  alkannin  is  taken 
from  Tschirch,  Angewandte  Pflanzeuanatomie,  The  United  States  Dispensatory 
and  The  Century  Dictionary. 
2Engler  &  Prantl,  "  Pflanzen  familien,"  43a  ;  73,  113,  124,  127. 
