254 
The  IHcroseope — Hints  to  Beginners. 
r  Am.  Jour  Pharm. 
t      ]May,  1882. 
is  done  by  holding  the  circle  between  the  thumb  and  forefinger  of  the  left 
hand  inclined  over  the  object,  and  letting  it  fall  gently  on  the  object  with 
a  needle  held  in  the  other  hand. 
Having  thus  temporarily  mounted  a  section,  transfer  it  to  the  stage  of 
the  microscope  and  first  apply  the  1-inch  power  and  shallow  eye-piece  ; 
this  will  give  a  general  outline  of  the  section,  provided  it  has  been  cut 
sufficiently  thin.  Presuming  that  such  has  been  obtained,  it  represents  a 
vertical  section  of  the  laurel  leaf,  and  will  show  the  different  shaped  cells, 
and  their  arrangement  with  each  other.  This  will  be  better  observed  if 
the  J-inch  power  is  used.  The  cells  of  the  outer  row  corresponding  to  the 
upper  blade  of  the  leaf  are  tabular  in  shaj)e,  and  look  not  unlike  bricks 
and  mortar;  below  these  is  seen  another  row  of  cells,  ovoid  in  shape,  and 
placed,  as  it  were,  on  end.  Within  these  cells  green  granules  will  be 
observed,  surrounded  by  a  mucilaginous  fluid ;  this  is  chlorophyll,  the 
fluid  being  the  protoplasm,  which  sometimes  gives  a  dimness  to  the  object 
unless  it  has  been  sufficiently  washed.  Occasionally  a  cavity  or  blank 
space  will  be  seen  in  a  section  of  the  leaf,  having  a  small  opening  at  the 
top  ;  this  is  an  air-chamber,  and  the  opening  above  is  a  stoma.  The  above 
section  may  be  taken  as  a  fair  example  of  the  parenchymatous  tissue.  If 
it  be  desired  to  mount  the  specimen  permanently,  it  had  better  be  put  for 
the  present  in  some  preservative  fluid,  such  as  a  mixture  of  spirit  and 
water,  and  labeled  what  it  is. 
In  the  cells  of  the  section  just  made  were  seen  chlorophyll  and  proto- 
plasm,but  there  is  a  third  and  very  important  substance  present  in  the  cells 
of  many  plants,  this  being  starch.  To  observe  the  granules  in  situ  make  a 
thin  section  of  a  piece  of  raw  potato,  place  it  on  a  slide  with  a  drop  or  two 
of  water,  cover  with  a  circle  as  already  described,  and  apply  a  ^  inch 
power.  The  granules  of  starch  will  be  seen  lying  in  the  cells,  and  show- 
ing that  the  potato  is  principally  composed  of  this  substance. 
When  starch  granules  are  viewed  by  polarized  light,  on  rotating  the 
analyzer  of  the  polariscope  they  show  a  beautiful  black  cross  ;  thi^  is  one 
of  the  best  tests  for  this  substance  in  adulterated  powders. 
To  view  the  cells  and  stomata  of  the  epidermis  place  a  portion  of  laurel 
or  ivy  leaf  in  strong  nitric  acid  to  which  a  little  water  has  been  added  ; 
boil  this  in  a  beaker  over  a  Bunsen  or  on  a  sand-bath,  and,  after  boiling 
for  several  minutes,  the  epidermis  will  separate  as  a  thin  skin  from  the 
remaining  portion  of  the  leaf ;  the  contents  of  the  beaker  should  then  be 
thrown  into  a  plate  full  of  water,  and  the  epidermis  removed  to  another 
vessel,  where  it  should  be  well  washed ;  when  thoroughly  freed  from  the 
acid,  cut  off  a  small  piece  and  place  it  on  a  slide  in  the  usual  manner,  and 
view  first  with  a  1-inch  and  then  with  ^-inch  power ;  this  will  give  a 
capital  view  of  the  epidermal  cells  and  stomata,  the  latter  being  made  up 
of  two  semi-lunar  cells  placed  together. 
Spiral  vessels  will  be  found  in  common  garden  rhubarb  ;  a  good  way  to 
obtain  these  is  to  peel  off  a  few  strips  from  the  stalk  of  the  plant,  let  them 
macerate  in  water  for  a  few  days,  then  with  the  finger  and  thumb  separate 
the  soft  portions  from  what  seem  like  stout  threads ;  take  one  of  these, 
place  it  in  a  watch  glass  or  small  porcelain  dish  with  a  little  water  in  it, 
and,  with  a  needle  in  each  hand,  gently  tease  out  this  thread.    This  will 
