TAXONOMY 
201 
less uniformly throughout this region but as the cell matures these 
coalesce, until, in a very old cell, a huge glycogen vacuole may be seen 
occupying most of the interior, with the cytoplasm and nucleus 
pushed up against the cell wall and forming there a very narrow layer. 
Fig. 82. — Yeast, Saccharomyces cerevisice, the variety known as brewers’ bot- 
tom yeast; a, spore formation; b, elongated cells. ( After Schneider, Pharmaceu- 
tical Bacteriology.) 
Yeast plants grow in dilute saccharine solutions containing dis- 
solved nitrogenous substances such as beerwort, Pasteur’s solution, 
grape juice, etc. Here they are constantly wasting away and as 
constantly being built up. The question may well arise: “How 
do they obtain the material necessary for growth and repair?” The 
answer, in a general way, is not difficult. The fluid in which they 
live is a solution of sugars and of nitrogenous and other matters. 
