472 
Calcium  Oxalate  Crystals. 
/Am.  Jour.  Pharm. 
I     October,  1901. 
R.  von  Wettstein  in  a  study  of  the  Umbelliferae  has  shown  that 
the  presence  and  distribution  of  calcium  oxalate  crystals  are  import- 
ant factors  in  systematic  work,  at  least  in  this  family,  and  my  own 
studies  of  the  Solanaceae  also  tend  to  confirm  this  view.  It  may 
also  be  noted  that  soil  conditions  do  not  seem  to  influence  the 
amount  of  this  salt,  i.  e.  a  plant  growing  in  silicious  soil  will  con- 
tain about  the  same  amount  as  one  growing  in  calcareous  soil.  I 
have,  however,  already  referred  to  the  fact  that  when  fungi1  are 
growing  on  plants  there  is  likely  to  be  a  decrease  in  the  number 
of  calcium  oxalate  crystals  usually  present. 
Calcium  oxalate  occurs  in  plants  in  either  the  monoclinic  or 
tetragonal  system.  The  crystals  of  the  monoclinic  system  are 
rather  widely  distributed  and  consist  of  Ca  C204  -f-  3  to  6  mole- 
cules of  H20 ;  while  those  of  the  tetragonal  system  occur  less  fre- 
quently and  the  salt  has  the  formula  Ca  C204  -f  1  to  2  molecules 
of  water.  It  is  rather  interesting  to  note  that  while  both  forms  of 
crystals  may  be  obtained  in  even  the  same  solution  artificially,  that 
in  nature  the  one  form  or  the  other  is  constant  for  the  species. 
Various  explanations  have  been  offered  showing  under  what  condi- 
tions the  two  forms  of  crystals  arise.  Haushoper  states  that  the 
tetragonal  crystals  are  formed  in  a  neutral  or  alkaline  solution, 
whereas  the  monoclinic  crystals  require  an  acid  solution  for  their 
formation.  Kny  believes  that  when  there  is  more  calcium  in  pro- 
portion to  the  oxalic  acid,  tetragonal  crystals  are  formed,  but  when 
the  proportions  are  reversed  then  crystals  of  the  monoclinic  system 
arise.  The  observations  of  Kohl  tend  to  confirm  the  studies  of 
Kny. 
While  calcium  oxalate  crystallizes  in  these  two  systems,  it  is 
highly  probable  that  but  one  of  these  systems  is  represented  by  our 
vegetable  drugs,  viz.,  the  monoclinic  system,  which  includes  a  num- 
ber of  forms  as  follows  : 
(1)  Rosette  aggregates,  or  what  are  commonly  termed  rosette- 
shaped  crystals. 
(2)  Prisms,  pyramids  and  elongated  or  irregular  hexagonal- 
shaped  crystals. 
(3)  Crystal-fibers. 
(4)  Raphides. 
1  Kraemer  in  Proc.  A.  Ph.  A.,  1898,  p.  297. 
