156 
ON  NITROGEN  IN  MANURES  AND  SOIL. 
nently  favor  vegetation.  He  now  shows,  by  decisive  experi- 
ments. 
(1.)  That  the  amount  even  of  ternary  vegetable  matter  pro- 
duced by  a  plant  depends  absolutely  upon  the  supply  of  assimi- 
lable nitrogen  (ammonia  and  nitrates.)  A  plant,  such  as  a 
sunflower,  with  a  rather  large  seed,  may  grow  in  a  soil  of  recently 
calcined  brick,  watered  with  pure  water,  so  far  as  even  to  com- 
plete itself  by  a  blossom ;  but  it  will  only  have  trebled  or  quad- 
rupled the  amount  of  vegetable  matter  it  had  to  begin  with  in 
the  seed.  In  the  experiments,  the  seeds  weighing  0-107  grammes, 
in  three  months  of  vegetation  formed  plants,  which  when  dried, 
weighed  only  0-892  grammes, — a  little  more  than  trebling  their 
weight.  The  carbon  they  had  acquired  from  the  decomposition 
of  carbonic  acid  of  the  air  was  only  0-114  grammes ;  the  nitrogen 
they  had  assimilated  from  the  air  in  three  months  was  only 
0-0025  grammes. 
(2.)  Phosphate  of  lime,  alkaline  salts  and  earthy  matters  indis- 
pensable to  the  constitution  of  plants  exert  no  appreciable  action 
upon  vegetation,  except  when  accompanied  by  matters  capable 
of  furnishing  assimilable  nitrogen.  Two  plants  of  the  same  kind, 
grown  under  the  same  conditions  as  above,  but  with  the  perfectly 
sterile  soil  adequately  supplied  with  phosphate  of  lime,  alkali  in 
the  form  of  bicarbonate  of  potash,  and  silex  from  the  ashes  of 
grasses,  resulted  in  only  0-498  grammes  of  dried  vegetable 
matter,  from  seeds  weighing  0-107  grammes;  and  had  acquired 
only  0-0027  grammes  of  nitrogen  beyond  what  was  in  the 
seeds. 
(3,)  But  nitrate  of  potash  furnishing  assimilable  nitrogen  as- 
sociated with  phosphate  of  lime  and  silicate  of  potash,  forms  a 
complete  manure,  and  suffices  for  the  full  development  of  vegeta- 
tion. Parallel  experiments  with  nitrate  in  place  of  bicarbonate 
of  potash,  resulted  in  the  vigorous  growth  of  the  sunflower  plants, 
and  the  formation  of  21-248  grams,  of  organic  matter,  from  seeds 
weighing  as  before  only  0407.  This  21-111  grams,  of  new  vege- 
table matter,  produced  in  three  months  of  vegetation,  contained 
8-444  of  carbon  derived  from  the  carbonic  acid  of  the  air,  and 
0-1666  grams,  of  nitrogen.  The  1.4  grams,  of  nitrate  of  potash 
supplied  to  the  soil  contained,  0-1969  grams,  of  nitrogen,  leaving 
