1897 THE MICROSCOPE. 167 
potash to give yellow reactions. Iodine possesses the prop- 
erty of turning starch and amyloid bodies blue, and so is 
generally applied to sections of the apothecia, when the asci 
are transformed from their plain semi-transparency to a 
delicate blue, thus rendering them at once visible, and 
their forms and positions may be easily ascertained. The 
lime and potash tests are generally used on the thallus or 
leaf-like portion of the lichen, some-times on the surface 
only, and at others on the medullary layer. 
Mounting Medium.—An adhesive material for labelson 
glass, or for fastening opaque objects for the microscope, 
is this; ‘Take 120 grains of gum arabic and dissolve it in 
a quarter ofa litre of water. Dissolve thirty grains of 
powdered gum tragacanth ina similar quantity of water. 
After a few hours, shake the latter solution until it froths, 
and mix with the former. Strain the mixture through 
linen, and afterwards add to it 150 grams of glycerine, pre- 
viously mixed with 2'2 grams of oil of thyme. 
Glycerine.—Is one of the most useful of mounting med- 
iums, but a difficulty is usually experienced with it when 
ringing. This may be overcome by using gum damar 
dissolved in benzoline instead of the usual gold-size. 
CORRESPONDENCE, 
Staining Vegetable Cells.—I am working now on the 
resting nucleus, and kanyokinetic figures, in vegetable 
cells of the onion, but am sort of groping in the dark, not 
knowing the length of time for fixing, staining, etc. 
Iam using Fleming’s chrom-osmic-acetic acid solution 
for fixing, imbedding in paraffine, haematoxlin stain, but do 
not meet with first class results. Would like suggestions. 
—I. Percy Brackman, Sanpy Hoox, Conn. 
Specimens.—From time to time I have sent little notices 
which you have very kindly used, Ihave sent away quite 
a number of specimens after each publication. This I am 
glad to do and for those little quarts crystals which seem 
to please, I have had repeated calls.— W. S. Berxman. 
