CONTRIBUTIONS  TO  THE  PHYSIOLOGY  OF   THE  SPIKACEj2.  61 
Thus  the  distillate  obtained  from  the  herbaceous  spiracece, 
gathered  in  June,  contains  salicylic  acid  and  no  hydrocyanic  acid, 
while  that  of  the  shrubby  plants  contains  hydrocyanic  and  no 
salicylic  acid.  The  distillates  from  the  leaves  and  roots  of  sp. 
ulmaria  from  the  entire  plant  of  sp.  digitata,  sp.  lobata,  sp.  fili- 
pendula,  contain  salicylic  acid.  The  distillates  from  sp.  aruncus, 
sp.  sorbifolia,  sp.japonica,  contain  hydrocyanic  acid.  Neither  of 
these  acids  are  found  in  the  distillates  from  sp.  levigata,  sp.  acu- 
tifolia,  sp.  ulmifolia,  or  sp.  spulifolia. 
The  author  directs  attention  to  the  fact  that  the  leaves  of  sp. 
sorbifolia  and  those  of  sp.  aucuparia  are  remarkably  similar,  and 
that  the  leaves  of  sp.  aruncus,  which  are  of  a  very  complex  kind, 
have  the  same  typical  character  of  form.  On  comparing  the 
leaves  of  sp.  filipendula  and  of  sp.  ulmaria  with  those  of  the  above 
named  members  of  this  family  the  analogy  in  form  is  obvious. 
The  other  two  herbaceous  spiracerc,  sp.  lobata  and  sp.  digitata, 
are  characterized  by  a  more  simple  form  of  leaf;  but  this  may 
be  assumed  to  be  the  fundamental  form  of  the  more  complex 
leaves.  These  herbaceous  spiracea)  are  further  chemically  char- 
acterized by  the  fact  that  on  distillation  with  water  they  yield 
salicylic  acid. 
If,  then,  the  assumption  is  correct  that  the  salicylic  acid  found 
originates  from  salicin  and  the  hydrocyanic  acid  from  amygdalin, 
the  occurrence  of  these  two  substances  in  this  family  is  a  fact 
worthy  of  attention,  for  both  of  them  are  conjugate  compounds 
containing  a  sugar.  Both  suffer  this  remarkable  change  in  con- 
tact with  emulsine.  Salicin  splits  up  into  saligenin  and  sugar  ; 
amygdalin  into  hydrocyanic  acid,  hydruret  of  benzoyle,  and  sugar. 
Saligenin,  by  assimilating  two  equiv.  of  oxygen  and  separation 
of  two  equiv.  of  hydrogen,  passes  into  salicylic  acid,  which  may 
be  thus  directly  formed  from  salicin.  But  further,  salicylic  acid 
is  isomeric  with  benzoic  acid,  which  is  formed  from  hydruret  of 
benzoyle  by  the  assimilation  of  two  equiv.  of  oxygen.  Again, 
saliretin  is  isomeric  with  hydruret  of  benzoyle,  which  is  formed 
from  saligenin  by  the  separation  of  two  equiv.  of  water. 
This  relation  which  appears  to  exist  between  the  structure  of 
the  plants  and  the  chemical  substances  which  occur  in  them,  the 
author  proposes  to  express  by  the  term  4<  isomophism  of  organic 
nature,"  regarding  here  instead  of  the  actual  replacement  of  one 
