Cytological Observations on the Yeast Plant. 
BY 
HAROLD WAGER, F.R.S., 
AND 
ANNIE PENISTON. 
With Plates VI—X, and a Figure in the Text. 
T N a former paper by one of us (Wager, ’98) an interpretation of the 
various structures observed in the Yeast Plant was put forward, which 
reconciled many of the diverse opinions then held, and placed the whole 
problem of the morphology of the nucleus and its behaviour during division 
and spore-formation on a more satisfactory and definite basis. 
In that paper it was pointed out that the deeply stained granule 
described by most of the previous observers as a nucleus is a homogeneous 
body, often so closely surrounded by granules as to give it the appear¬ 
ance of a granular nucleus, and that in addition there is present in 
healthy yeast cells a more or less distinct vacuole, easily seen in the living 
condition, which contains a granular substance. It was suggested that 
as these two organs of the cell are so closely bound up with each other, we 
were justified in regarding them as representing the nucleus of the higher 
plants. 
This interpretation has been criticized by various observers in 
a number of interesting memoirs, but so many different views have been 
put forward, that instead of giving a more coherent and precise knowledge 
of the structure of the nucleus, they further enhance the pre-existing 
confusion. 
Macallum, in a very interesting paper (’99), found that the yeast cell 
contains, at the beginning of fermentation, granules and vacuoles grouped 
irregularly and varying in number and character, but as a rule only one 
large vacuole. The basis of these granules seems to be a proteid substance, 
which may vary in its character during the various stages of fermentation. 
In the earlier stages they appear to have a fatty nature, although the 
reaction for fat is not intense enough to suggest a purely fatty composition. 
[Annals of Botany, Vol. XXIV. No. XCIII. January, 1910.] 
