1 34  Preserving  the  Color  of  Dried  Plants.  {  AmSiJa°rcb,  fit™' 
except  with  some  members  of  the  Umbelliferae,  which  turned  dark 
when  thus  treated. 
I  had  not  the  opportunity  of  making  further  experiments  with 
them,  and  do  not  know  their  behavior  when  dried  in  paper  without 
the  aid  of  oxalic  acid. 
The  leaves  of  Phytolacca  decandra,  under  ordinary  circumstances, 
turned  to  a  very  dark  color  ;  when  dried  by  the  aid  of  a  3  per  cent- 
solution  of  oxalic  acid  they  remain  green. 
The  leaves  of  Geranium  macuiatum  commonly  turn  reddish- 
brown  ;  when  preserved  with  3  per  cent,  of  the  acid  they  remain 
green. 
The  leaves  and  petals  of  Baptisia  tinctoria  almost  invariably  turn 
black  when  dried  in  the  ordinary  way ;  when  preserved  with  3  per 
cent,  oxalic  acid,  the  change  is  much  less  pronounced  and  the  petals 
remain  yellow. 
In  all  specimens  the  color  of  the  petals  was  unchanged. 
The  results  which  I  have  obtained  by  this  process  lead  me  to  the 
conclusion  that  it  may  be  employed  with  decided  advantage  in 
almost  all  cases,  and  I  will  briefly  state  the  method  I  have  employed  : 
Heavy  gray  felt  paper  was  thoroughly  saturated  with  a  3  per  cent, 
solution  of  oxalic  acid,  and  dried.  This,  when  done  at  ordinary 
summer  temperature,  required  about  twelve  hours.  Directly  between 
the  thus  prepared  paper  I  placed  the  plant ;  in  case  the  petals  were 
very  delicate,  they  were  protected  by  a  very  thin  piece  of  paper  to 
prevent  imprints  from  the  rough  felt  paper.  The  latter  was  changed 
once  in  twenty-four  or  thirty-six  hours,  until  the  plant  was  thor- 
oughly dried,  and  it  was  then  mounted  in  the  ordinary  way.  If 
possible,  the  plants  should  be  placed  in  the  press  at  the  time  of 
collection,  or  carried  in  an  air-tight  box  and  moistened  before 
pressing. 
Up  to  the  present  date  I  have  not  had  the  opportunity  of  study- 
ing by  experiments  to  what  extent  plant  colors  are  really  injured 
by  ammonia,  but  I  hope  to  be  able  to  report  upon  this  question  at  a 
subsequent  date. 
Philadelphia,  February,  1896. 
