the Yeast Plant. 
69 
stains the volutin granules black and the nucleolus and chromatin network 
violet. Haemalum is the only stain which invariably differentiates both 
sets of granules, the chromatin granules being reddish blue and the c meta¬ 
chromatin ’ black. 
Iron. 
Macallum (’ 95 ) has shown that various parts of the vegetable cell 
contain iron in organic combination. It may occur in any part of the cell, 
but is most abundant in the nucleus and nuclein constituents and in such 
organs as the pyrenoid and in the chromatophore. It is found also in 
various species of Saccharomyces. If cells of 5 . cerevisiae are treated with 
glycerine-ammonium sulphide solution for several days at a temperature of 
6o° C., their cytoplasm acquires a greenish tint due to the iron. Sometimes, 
however, the reaction may appear only in a few granules scattered through 
the cytoplasm. In cells subjected to the action of sulphuric acid alcohol 
and subsequently treated with acid potassium ferrocyanide solution, the 
presence of iron is shown by a faint blue colour in their cytoplasm with 
sometimes blue granules. In S'. Ludwigii treated in the same way, the 
stainable substance is found chiefly at the periphery of the vesicles and in 
a substance which constitutes corpuscles of a nucleolar character, large 
spherical elements which in the glycerine-ammonium sulphide mixture 
appear darker green than the surrounding cytoplasm. 
In a later paper (’ 99 ) the author states that after ten days at the 
latest in the glycerine-ammonium sulphide solution, the presence of 
f masked ’ iron is distinctly demonstrated in the one or more corpuscles 
which may be present in each cell (S. Ludwigii and 5 . cerevisiae ), in the 
walls of the vacuoles, and in the cytoplasm generally. 
We have found the distribution of organic iron in yeast cells, when 
examined with the acid ferrocyanide solution after the action of sulphuric 
or nitric acid alcohol, very much as described by Macallum (’ 95 ), but the 
coloration was very slight. When the cells were treated with 5 per cent, 
solution of haematoxylin (Macallum, ’ 97 ), however, instead of the ferro¬ 
cyanide solution, the staining was much stronger, and, although the colora¬ 
tion was diffuse, it was possible to distinguish the nucleolus clearly in 
nearly all cells under high powers of the microscope. Specimens hardened 
in alcohol were used. These were placed in an alcoholic solution of nitric 
or sulphuric acid (4 parts H 2 S 0 4 and 100 parts methylated spirit, or 
3 parts strong HN 0 3 to 100 parts spirit) for twenty-four to thirty hours 
at a temperature of 35° C. to unmask the iron. They were then washed 
in alcohol and placed for a short time in the haematoxylin solution. After 
this they were washed several times in distilled water, then in alcohol, and 
finally mounted in balsam or dilute glycerine. Wherever iron exists in the 
cell, the coloration is slaty blue, the yellowish coloration in other parts of 
the cell which comes out on washing in the water and alcohol being due 
