The  Hills  H.vperiments. 
309 
one,  though  other  salts  of  manganese  used  (oxide,  carbonate, 
sulphate,  phosphate,  and  nitrate)  had  a negative  or,  possildy, 
favourable  influence.  Putting  the  results  of  the  two  years 
together,  it  would  appear  that  it  is  to  the  iodine,  and  not  to 
the  metal  with  which  this  is  combined,  that  the  ill  effects 
are  due,  and  that  the  iodides  generally  are  harmful,  even  if 
applied  at  the  rate  of  1 cwt.  per  acre.  As  regards  the  second 
part  of  the  experiment — that  with  oxides  of  the  foregoing 
metals — it  has  to  he  observed  that  in  every  case  the  influence 
was  a beneficial  one.  The  salts  were  used  at  the  rate  of 
2 cwt.  per  acre.  Lithium  oxide,  though  producing  the  shortest 
straw — owing  to  the  early  retardation  always  noticed — gave 
the  highest  return  l)oth  of  corn  and  straw,  and  it  would  appear 
that,  though  there  is  at  first  a “caking”  of  the  surface  soil,  this 
has,  in  the  end,  no  harmful  result.  Between  the  oxides  of 
manganese,  potassium,  and  sodium  respectively  there  is  little 
to  choose.  In  previous  experiments  conducted  on  wheat  in 
1901,  lithium  oxide  and  potassium  oxide  were  shown  to  have 
a beneficial  effect,  while  the  experiments  of  1902  brought  out 
a like  advantage  from  the  use  of  maganese  oxide.  The  present 
experiments  are  therefore — while  differently  conducted — quite 
in  harmony  with  the  former  ones,  and  the  conclusions  may 
therefore  he  drawn: — 
1.  That  the  iodides  of  the  metals  manganese,  potassium, 
sodium,  anti  lithium,  when  used  even  at  the  rate  of  1 cwt.  per 
acre,  have  an  injurious  effect  upon  wheat,  this  being  most 
marked  with  the  iodide  of  manganese. 
2.  That  the  oxides  of  the  metals  manganese,  potassium, 
sodium,  and  lithium,  when  used  at  the  rate  of  2 cwt.  per  acre, 
have  a beneficial  influence  vipon  wheat,  this  being  most  marked 
with  the  oxide  of  lithium. 
2.  The  influence  of  the  Iodides  and  Oxides  of  Manganese^ 
Potassium,  Sodium,  cmd  Lithium  on  Barley. 
These  experiments  were  conducted  almost  similarly  to  those 
just  set  out  on  wheat,  the  applications  being  mixed  with  the 
top  4 Ih.  of  soil,  and  not  given  in  solution.  The  variety  of 
barley  used  was  “ Goldthorpe,”  sown  on  Aj)!-!!  17,  1903,  twelve 
seeds  per  pot,  the  pots  being  of  eartlienware  and  each  set  in 
duplicate.  After  the  plants  had  come  up  they  were  i-educed  to 
six  in  each  pot.  The  applications  were  made  in  all  cases  at  the 
rate  of  2 cwt.  per  acre. 
Though,  with  but  slight  exception,  the  plants  all  came  up 
well,  very  shortly  afterwards  the  whole  of  the  plants  treated 
with  iodides  began  to  look  sickly  and  to  die  away.  Where 
plants  did  survive,  their  growth  was,  as  has  been  noticed  before 
exceptional,  owing  no  doubt  to  the  greater  space  left  for  them 
