^'ju°iy?if9h3arm*}      Strophanthus  Seed  of  Commerce.  347 
is  produced  and  the  ultimate  shade  that  it  reaches,  in  some  cases 
the  tint  being  carmine  red,  and  in  others  rose  or  bluish  red.  These 
tints  seem  constant  for  each  variety,  and  a  little  practice  soon 
renders  it  comparatively  easy  to  discriminate  between  the  seeds  from 
different  sources,  especially  when  taken  in  conjunction  with  the 
slight  external  differences  in  the  shape  of  the  seed,  the  greater  or 
less  density  of  its  hairy  coat,  and  the  more  or  less  regularity  in  the 
arrangement  of  the  hairs  in  lines. 
It  must  not,  however,  be  taken  for  granted  that  seeds  giving  the 
red  reaction  are  not  poisonous,  for  M.  Arnaud  has  shown  that  the 
seeds  of  S.  glaber  (which  give  a  red  reaction)  contain  a  considerable 
quantity  of  ouabain,  a  glucoside,  similar  to  strophanthin  in  its 
physiological  properties,  but  two  to  four  times  stronger  in  its  action 
on  small  animals.  This  glucoside  gives  no  coloration  with  concen- 
trated sulphuric  acid  for  a  considerable  time,  and  then  only  a  pale 
brown  tint,  nor  do  the  other  mineral  acids  produce  any  color  reac- 
tion with  it.  It  is  obvious,  therefore,  that  as  it  is  at  present  unknown 
whether  all  the  seeds  giving  the  red  reaction  are  poisonous  or  not, 
and  that  as  some  may  be  more  poisonous  than  the  official  seeds,  we 
have  here  a  factor  that  adds  considerably  to  uncertainty  of  action  of 
preparations  made  from  mixed  seeds. 
The  practical  bearing  of  the  facts  already  brought  forward  may 
be  summarized  as  follows  :  It  is  highly  desirable,  owing  to  the 
occurrence  of  the  seeds  of  different  species  of  Strophanthus  in  com- 
merce, and  to  the  occasional  mixture  of  such  seeds,  that  seeds  should 
always  be  purchased  in  the  follicle,  and  that  a  seed  from  each  follicle 
should  be  tested  with  concentrated  sulphuric  acid.  In  no  other  way 
can  a  reliable  preparation  be  made,  since,  even  if  strophanthin  were 
used,  at  present  there  is  no  ready  means  of  detecting  ouabain  in 
the  presence  of  strophanthin,  should  the  latter  be  prepared  from 
mixed  Strophanthus  seed. 
It  may  be  useful  to  append  here  a  few  details  concerning  the 
general  features  of  the  African  species  of  this  genus,  in  the  hope 
that  future  travellers  in  Africa  may  endeavor  to  clear  up  the  botani- 
cal sources  of  the  varieties  or  seed  occurring  in  commerce. 
The  species  of  the  genus  Strophanthus  are  mostly  climbing 
shrubs,  although  some  appear  to  be  small  trees  or  erect  shrubs.. 
The  leaves  are  opposite  and  more  or  less  elliptical,  hairy  in  some 
species  and  glabrous  in  others.    The  flowers  are  often  terminal,  but 
