AmMa™h$mm' }    Preserving  the  Color  of  Dried  Plants.  1 3 3 
Since  then  I  have  had  occasion  to  study  the  value  of  Nienhaus' 
process,  and  have  found  that  not  only  the  petals  are  well  preserved, 
but  that  a  3  per  cent,  solution  will  also  preserve  the  color  of  the 
leaves.  In  the  hope  that  the  results  may  be  of  interest  to  collectors 
of  plants,  I  think  it  proper  to  bring  it  to  their  notice. 
Several  specimens,  which  had  been  dried  by  the  aid  of  1  per  cent, 
oxalic  acid,  did  not  give  me  as  good  results  as  I  had  hoped  to  ob- 
tain, and  I  then  determined  to  study  the  value  of  different  strengths 
of  the  solution,  and  find  out  which  would  be  most  suitable  to  be 
employed  in  average  cases. 
For  this  purpose  I  saturated  some  gray  felt  paper  with  solution  of 
oxalic  acid,  varying  in  strengths  from  I  to  5  per  cent.,  and  dried. 
Leaves  of  different  texture  were  selected,  dried  between  the  thus 
prepared  paper  at  ordinary  temperature,  changing  paper  once  in 
twenty-four  hours. 
Leaves  of  a  thin  texture  were  well  preserved  with  a  2  per  cent, 
solution ;  not  so  well  with  that  of  1  per  cent.    Those  dried  between 
3  to  5  per  cent,  paper  did  not  differ  materially  in  appearance  from 
those  dried  with  that  of  2  per  cent,  strength. 
Leaves  of  a  thick  texture  were  best  preserved  with  3  per  cent,  of 
the  acid,  although  the  4  and  5  per  cent,  solutions  showed  no  disad- 
vantage. 
The  leaves  of  aquatic  plants  were  best  preserved  with  2  or  3 
per  cent,  of  acid  ;  the  I  per  cent,  specimens  turned  dark,  and  with 
4  or  5  per  cent,  they  were  almost  black  in  one  case,  while  in  other 
aquatics  I  could  observe  no  difference  between  any  of  the  speci- 
mens ;  they  all  had  kept  well. 
These  results  suggested  to  me  that  paper  saturated  with  a  3  per 
cent,  solution  of  oxalic  acid  might  be  used  with  more  advantage  for 
the  majority  of  plants  than  a  1  per  cent,  solution,  as  recommended 
by  Nienhaus.  It  is  not  unlikely  that  the  kind  of  drying-paper  used 
influences  the  results  to  some  extent. 
Nienhaus  recommended  filter-paper  to  be  employed ;  in  fact,  the 
heavy  felt  paper  mostly  employed  in  this  country  is  not  often  used 
in  Germany  for  drying  purposes  ;  the  botanists  there  prefer  a  very 
much  thinner  gray  paper. 
In  almost  all  cases  where  a  3  per  cent,  solution  of  oxalic  acid  was 
employed,  I  have  obtained  satisfactory  and  encouraging  results, 
