The  Hills  E.vpenments. 
313 
3.  Water-culture  Experimcntfi  on  Barley  with  the  Iodides 
and  0.rides  of  Manganese  and  Lithium. 
As  a complement  to  the  foregoing,  a series  of  experiments 
in  water-culture  with  the  iodides  and  oxides  of  manganese 
and  lithium  was  instituted,  chiefly  with  the  view  of  seeing 
what  influence  these  salts  had  on  the  root-growth  of  the  barley 
plant.  Barley  seed  was  germinated  on  blotting  paper  and  then 
transferred  to  glass  cylinders  where  it  was  fed  with  a nutritive 
solution  composed  as  follows: — 
Potassium  cliloride  . . 2 grammes. 
Magnesium  sulpliate  . .2  „ 
Potassium  j)hosphate  (.acid)  . 2 „ 
Calcium  nitrate  . . .8  „ 
Distilled  Water  . . .6  litres,  with  a few  drops 
of  chloride  of  iron. 
In  each  of  ten  cylinders,  1,000  c.c.  of  the  altove  solution 
were  put,  and  to  them  additions  were  made  as  follows; — 
1 and  2 no  further  addition. 
•S. 
•10 
grammes 
Iodide  of  manganese  (Mnl.^). 
4. 
■20 
11  11 
5. 
•10 
Iodide  of  lithium. 
G. 
■20 
»1  51 
7. 
•10 
u 
Oxule  of  manganese  (Mn,0^). 
8. 
•20 
n 
9. 
•10 
jj 
0.xide  of  litliium. 
10. 
•20 
5 5 5 5 
In  the  case  of  the  insoluble  salts,  oxide  of  manganese  and 
oxide  of  lithium,  these  were  ground  up  as  finely  as  possible  and 
then  added  to  the  cylinders. 
The  untreated  barley  plants  (cylinders  1 and  2)  made  good 
progress,  and  were  strong  and  healthy;  the  roots  developed 
quickly,  and  soon  filled  the  cylinder.  With  manganese  iodide, 
however,  a thin  delicate  root  was  produced,  Itut  with  marked 
absence  of  fine  rootlets  except  near  the  surface.  Subsequently 
there  was  just  the  one  long  taj)  root,  extending  three-quarters 
of  the  way  down  the  cylinder,  with  Imt  few  side  shoots.  The 
stronger  the  solution  was,  the  more  was  this  shown.  After  a 
time  the  foliage  of  the  plant  turned  brown,  and  finally  died 
away  alfogether.  Much  the  same  happened  with  iodide  of 
lithium,  except  that  here  the  tap  root  was  thick,  l)ut  short  and 
stunted,  and  sent  out  a fair  number  of  side  shoots.  The  foliage, 
however,  died  off  after  a time,  just  as  it  had  done  with 
manganese  iodide.  Manganese  oxide,  on  the  other  hand,  gave 
a root  that  showed  good  growth,  with  a considerable  number 
of  root  hairs,  these  being  marked  by  a fineness  not  ol)serval)le 
in  the  untreated  series.  The  manganese  oxide  clung  about  the 
rootlets  and  seemed  to  be  deposited  on  them.  With  lithium 
oxide  the  root,  as  with  lithium  iodide,  was  thick  and  stunted, 
but  considerably  better  in  growth  than  was  the  case  with  the 
