156 
QUICKSILVER. 
by  endosmosis  through  the  bark  cells.  Dr.  Grahame  says  that  by 
every  such  process  the  membrane  of  these  cells  is  thinned  and 
dissolved ;  that  the  endosmosis  is  different  for  every  different 
membrane  ;  and  that  the  force  of  endosmosis  is  altered  not  only 
by  the  different  nature  of  the  substances  going  into  the  cell,  but 
also  by  the  nature  of  the  sap  in  the  cell  itself. 
The  author  considers  these  facts,  as  made  out  by  Mr. 
Grahame,  to  be  the  starting  point  of  a  new  era  in  the  physiology 
of  nutrition.    No  one  has  yet  taken  up  the  matter  and  pointed 
out  the  uses  of  these  discoveries,  and  it  was  sufficient  at  present 
that  Dr.  Grahame  shows  that  any  slight  difference  in  the  compo- 
sition of  a  membrane,  or  of  the  contents  of  a  cell,  will  be  suffi- 
cient cause  for  a  decided  difference  in  the  nature  of  the  food  in- 
troduced into  it.  The  point  of  a  rootlet  is  of  very  different  struc- 
ture from  its  upper  part.  It  serves  only  for  the  growing  out  of 
the  rootlet,  whose  cells  are  formed  in  the  upper  part.    Many  of 
the  cells  run  into  short  hollow  hairs,  which,  like  the  cells,  have 
a  very  thin  membrane.   The  fluid  taken  in  by  the  rootlet,  after 
a  time  destroys  the  outer  layer  of  cells,  and  the  second  layer 
comes  into  play,  but  the  constant  production  of  new  cells  in  the 
interior  causes  the  rootlet  to  increase  in  size.    Passing  from  cell 
to  cell  the  fluid  becomes  changed  into  sap  ;  but  the  sap  differs 
in  every  cell,  and  each  cell  around  one  well  filled  gets  out  of  it 
a  different  kind  of  food.    The  author  contends  that  it  is  not 
possible  to  get  into  a  plant  anything  that  is  a  poison  to  it.  The 
result  will  be,  if  poisonous  matter  is  present,  that  the  outer 
layer  of  cells  will  be  destroyed,  succeeding  layers  presenting 
themselves,  and  also  being  destroyed  so  long  as  the  poison  ex- 
ists around.    If  the  poison  gets  into  the  outer  cells  before  they 
are  wholly  destroyed,  it  will  not  be  taken  up  so  readily  as  a 
nutritious  liquid  ;  and  in  any  case,  after  traversing  a  few  rows 
of  cells,  all  poison  will  be  retained,  whilst  other  portions  of  the 
plant  will  remain  uninjured. — Proceedings  of  the  Brit.  Assoc,  a 
Manchester,  Sept  1861. 
QUICKSILVER. 
The  magnitude  of  our  Quicksilver  export  the  present  year  is 
calculated  to  attract  attention.  Not  only  has  there  been  an  en- 
tire recovery  of  that  trade  from  the  low  ebb  it  had  reached  under 
