45 2  The  Apocynacece  in  Materia  Medica. 
may  be  aborted  in  this  or  other  regions.  Sometimes  larger  than 
the  neighboring  cells,  consequently  easily  seen  and  ordinarily  on  sec- 
tion ovoid  or  a  little -sinuous,  at  other  times  they  are  difficult  to  see 
because  of  their  complete  resemblance  with  the  neighboring  cells 
from  which  one  may  distinguish  them  in  longitudinal  section.  The 
walls  of  these  show  a  thin  membrane  like  the  neighboring  paren- 
chyma cells,  the  others  a  white  membrane  much  more  thick.  The 
contents  of  these  is  sometimes  granular  and  opaque,  at  other  times 
transparent,  or  oleo-resinous  and  the  consistence  very  thick,  rich  in 
caoutchouc.  In  the  free  state  the  aspect  of  the  liquid  is  a  white 
latex,  rarely  nearly  clear.  The  wall  is  formed  of  pure  cellulose, 
resisting  the  Amylobacter  ;  this  permits  the  separation  of  these  ves- 
sels by  maceration. 
Internal  Liber. — The  ligneous  fascicles  are  comprised  between  two 
liber  zones,  as  in  a  great  number  of  families.  But  here,  contrary,  to 
that  which  we  find  in  the  Cucubitaceae,  for  example,  the  internal 
liber  appears  independent.  It  shows  itself  in  the  medullary  region 
in  scattered  bundles,  sometimes  quite  remote  from  the  wood,  while 
the  external  liber  is  immediately  opposite  to  it.  There  is  a  great 
abundance  in  nearly  all  the  tissues  of  calcium  oxalate  in  two  forms: 
rhombohedrons  and  macles,1  sometimes  in  mass,  at  other  times  sepa- 
rate, and  their  localization  is  frequent  along  the  sclerotic  or  fibrous 
elements. 
Affinities. — The  single  character,  that  is  always  constant  in  the 
Asclepiadaceae,  the  cohesion  of  the  pollen  grains,  serves  to  distinguish 
it  from  the  Apocynaceae.  The  latter  likewise  in  certain  characters 
approaches  the  Loganiacese,  Rubiaceae,  Oleaceae  and  even  the  Gen- 
tianaceae. 
History. — The  European  Apocynacese,  Nerium  and  Vinca,  are 
native  and  known  in  the  most  ancient  times.  Hasselquist  supposes 
even  that  it  was  the  Rose-Laurel,  to  which  allusion  is  made  in  the 
first  psalm  of  David.  Dioscorides  was  acquainted  with  the  Penenches 
and  the  Nerium,  which  Apuleius  described  under  the  name  of  Rose- 
Laurel.  In  Arabia,  Avicenna  distinguished  two  varieties,  of  which 
the  one  (woody  and  spiny),  may  be,  according  to  Sprengel,  was  the 
1  Macles,  according  to  Storm outh,  "a  term  applied  to  'twin-crystals,'  which 
are  united  by  simple  contact  of  their  faces  by  interpenetration,  or  by  incor- 
poration, these  twin  forms  being  often  repeated  so  as  to  form  groups." 
G.  M.  B. 
