312 
The  Woburn  Pot-Culture  Kxperiments,  1903. 
lessened  towards  the  time  of  rii)ening.  The  iodide  seiles  were 
later  than  the  oxide  series  in  ripening,  bnt  eventnally  the 
measui’ements  of  straw  and  ear  were  made,  photographs  taken, 
and  the  produce  reaped  and  weighed.  The  photograph  (Fig.  2, 
page  311),  shows  the  relative  appearances  of  the  croi)S,  and  the 
results  of  the  measurements  and  weighings  are  given  in  Table 
II.,  page  310. 
The  two  untreated  pots  were,  unfortunately,  not  regular  in 
their  growth,  one  being,  from  some  reason,  better  than  the 
other,  and  producing  thirteen  ears  as  against  nine  ; hence,  strict 
comparison  as  regards  pro(h;ce*  is  not  possible. 
The  iodides  have  shown,  as  with  the  wheat,  a decidedly 
harmful  effect,  a number  of  plants  having  been  killed  off 
entirely,  and,  though  in  some  cases — notably  with  manganese 
iodide — a fair  return  of  corn  and  straw  was  obtained,  this  has 
been  due  to  the  abnormal  development  of  one  or  two  i)lants 
only.  Turning  to  the  experiments  of  1'.102  on  barley,  it  will  he 
found  that  when  manganese  iodide,  at  the  rate  of  2 cwt.  per 
acre,  was  used,  but  in  solution,  less  than  half  the  number  of 
plants  came  up,  though,  as  now,  the  actual  return  derived  from 
the  remaining  plants  was,  through  their  unusual  stimulation,  by 
no  means  small.  It  may  be  reasonably  concluded,  therefore, 
that  the  iodide  generally  cannot  he  used  for  l)arley  at  the  rate 
of  2 cwt.  per  acre,  at  least  without  producing  harm,  and  that 
here  again  the  evil  effect  is  due  rather  to  the  iodine  in  combi- 
nation than  to  the  particular  metal. 
On  the  other  hand — though,  as  stated,  the  figures  are  not 
strictly  comparable — it  would  not  appear  that  any  harm  or  any 
marked  good  has  been  the  result  of  treatment  with  the  oxides  of 
manganese,  &c.  In  the  case  of  wheat,  it  will  he  remembered, 
the  oxides  were  productive  of  some  l)enefit,  more  especially  tlie 
lithium  oxiile.  With  barley  the  litliium  oxitle  gave  a i)lant 
which  at  one  time  seemed  well  in  advance  of  the  otliers,  and 
the  yield  of  straw  was  decidedly  increased,  hut  not  tliat  of  grain. 
Lithium  oxide  produced  the  same  “caking”  of  top-soil  as  had 
l)een  noticed  with  wheat. 
Putting  the  results  together  we  come  to  the  following 
general  conclusions: — 
1.  That  ioditles  of  manganese,  potassium,  sodium,  and 
lithium,  when  applied  at  the  rate  of  2 cwt.  per  acre,  are 
harmful  to  the  barley  plant,  actually  destroying  a ])roportion 
of  the  plants  grown.  The  had  effect  is  more  pronounced  than 
with  wheat. 
2.  That  oxides  of  manganese,  potassium,  sodium,  and 
lithium  have  no  harmful  effect  on  barley,  hut,  on  the  other 
hand,  are  not  productive  of  direct  benefit,  except,  possibly,  in 
the  case  of  lithium  oxide. 
