Am.  Jour.  Pharm. 
October,  1920. 
Rhus  Venenata  DC, 
697 
medullary-rays  are  usually  one  and  two  cells  wide,  with  four  cells 
as  the  maximum  width.  As  stated  by  Solereder/  the  resin  canals, 
which  are  characteristic  for  the  plants  of  the  Anacardiaceae,  often 
extend  from  the  bast  region  and  penetrate  into  the  medullary  region, 
Fig.  I. — Transverse  section  of  young  stem  of  Rhus  venenata  DC.  Epidermis 
(ep) ;  cortex  (c) ;  rosette  crystals  of  calcium  oxalate  (r) ;  continuous  ring  of 
stereomatic  tissue  in  pericycle  (s);  phloem  (p);  resin  canals  (re);  cambium 
(ca) ;  xylem  (x) ;  wood  fibers  (wf) ;  and  tracheae  (t)  of  the  xylem ;  medullary 
rays  (mr);  pith  (m). 
where  they  end  blindly.  The  canals  are  narrow-branching  vessels 
filled  with  a  dark  reddish  brown  substance  of  a  resinous  nature. 
This  substance  responded  to  the  cyanin  test  for  resin.  It  did  not 
react  to  the  chemical  tests  for  gummy  lignin  as  noted  by  Youngken'* 
