the Yeast Plant. 
53 
granule which in the living condition is observed in the vacuole, (b) Concen¬ 
trated solution in 5 per cent, alcohol (Figs. 48,49). The nucleolus is sharply 
differentiated ; the peripheral cytoplasm is homogeneous. The vacuole 
is not visible, but its position is indicated by a number of refringent 
granules suggestive of a reticulum ; among these one or more larger granules 
are to be distinguished. 
7. Alcohol 30 per cent. (Figs. 42-4). The nucleolus shows clearly, but 
the vacuole is invisible, the cytoplasm being completely hyaline. The 
refringent granules appear to be scattered throughout the cell; the large 
granule, which in the living cell is situated towards the centre of the vacuole, 
is at one side of the cell (Fig. 42). In addition there are visible a number 
of smaller and much less refringent granules. 
8. Absolute Alcohol (Figs. 45—7). The nucleolus and vacuole are clearly 
visible ; the latter is often slightly contracted (Fig. 45). The cytoplasm is 
hyaline with refringent granules, and the large granule in the vacuole is 
prominent. 
Methods of Staining. 
As some of the existing confusion with regard to the various structures 
found in the yeast cell is undoubtedly to be attributed to the many different 
methods of staining that have been used to differentiate them, and to the 
tendency of certain observers towards the exclusive use of one method, 
it may be useful to give here some indication of the relative value of 
a number of the more important stains that have been found useful. We 
have found it best to make paraffin sections and stain them on the slide. 
The tube method of staining is not productive of good results, owing to the 
difficulty of controlling the staining and subsequent washing-out processes 
with precision. 
A useful method of manipulating a small quantity of yeast is that 
described by Wager (’ 98 ). The fixed yeast is spread on a slide in a little 
water, and allowed to dry up completely. It can then be manipulated with 
as much ease as paraffin sections. If the cells are well fixed, no contortion 
or displacement is brought about by drying up, and excellent preparations 
are obtained. 
The most reliable and effective results have been obtained with 
Heidenhain’s method of haematoxylin staining. We stain for eight to 
thirty-six hours in a 5 per cent, solution of haematoxylin in distilled water, 
after mordaunting for half an hour to three hours in a 2-J per cent, solution 
in distilled water of either ferric ammonium sulphate or potassium aluminium 
sulphate. The preparations are finally differentiated in the mordaunting 
solution. When the first of these mordaunts is used, a sharp differentiation 
of the nuclein-containing elements of the cell is obtained, while the second 
