of  the  Ashes  of  Plants. 
535 
stituent  of  the  dry  matter,  and  would  vary  with  the  increase  or 
decrease  of  the  latter  in  the  plant.  The  column  in  the  table 
which  represents  the  ash  on  the  dry  grasses  does  not  exhibit  the 
same  variations  as  the  one  which  precedes  it,  and  for  the  reason 
just  stated.  The  specimen  Dactylis  glomerata  in  its  different 
stages  of  flowering  and  seeded  is  a good  illustration  of  the  point 
in  question. 
The  preceding  table  contains  the  analysis  of  the  natural 
grasses. 
The  points  which,  in  examining  this  table,  strike  us  as  most 
worthy  of  remark  are  the  following  : — The  universally  high  per 
centage  of  silica  in  all  the  grasses.  This  is  a characteristic  of 
the  class  ; it  is  accompanied  with  an  equally  high  per  centage  of 
potash.  It  is  remarkable  that,  whilst  so  large  a quantity  of 
potash  is  found  in  the  ashes  of  these  plants,  there  is  scarcely  a 
portion  of  soda  as  such  ; there  is,  indeed,  more  or  less  of  chloride 
of  sodium  (common  salt),  together  with,  in  many  cases,  large 
quantities  of  chloride  of  potassium.*  Another  argument  is  hereby 
supplied  in  favour  of  the  view  which  supposes  the  non-essential, 
or  at  all  events  secondary  character,  of  soda  in  relation  to  vege- 
tation. 
The  specimen  of  annual  meadow-grass  (Poa  annua)  differs 
from  all  the  others  with  which  it  is  associated  in  this  table,  both 
in  the  low  per  centage  of  silica  and  the  corresponding  increase  in 
the  proportion  of  potash.  This  grass  is  also  peculiar  in  the  pro- 
portion of  ash,  which,  whether  calculated  on  the  natural  or  the 
dry  specimen,  is  peculiarly  low.f  Reserving  for  the  present  any 
further  observations  that  may  suggest  themselves,  we  pass  on  to 
the  description  of  some  other  plants,  which,  although  commonly 
called  grasses,  belong  to  other  and  different  natural  divisions. 
To  the  per  centage  of  water  and  ash  in  these  plants  the  same 
remarks  which  we  ventured  to  make  in  the  previous  case  of  the 
two  grasses  will  apply,  with  slight  modifications.  Having  large 
leaves  and  succulent  stems,  they  however  contain  more  water  than 
the  grasses  collected  at  the  same  dates. 
* The  chemical  reader  will  understand  that  where  the  quantify  of  chlorine  cor- 
responds with  the  proportion  of  soda  (sodium)  in  the  ash,  as  it  frequently  does,  it  is 
considered  to  be  combined  with  it;  if  it  falls  short,  soda,  as  such,  is  said  to  be  present; 
if,  on  the  contrary,  there  is  more  them  would  form  chloride  of  sodium,  it  is  put  down 
as  chloride  of  potassium.  When,  therefore,  the  latter  is  mentioned  in  the  analysis,  it 
precludes  the  presence  of  soda.  Although  there  are  many  circumstances  in  favour  of 
this  mode  of  stating  results,  it  is  never  insisted  upon  as  of  absolute  correctness,  but  as 
the  only  course  open  to  the  analyst. 
f Annual  meadow  grass  is  said  (see  Low's  Agriculture)  to  be  the  most  productive 
of  all  the  grasses.  Is  this  in  any  degree  to  be  attributed  to  its  more  moderate  mineral 
requirements  ? 
