PAALEOPHY TA 309 
Saccharomyces is also used in raising bread, being sold in the 
form of yeast cakes. This fungus causes the sugar in the bread 
to be converted into alcohol 
and carbon dioxide, and it is 
the production of the carbon | 
dioxide that is responsible for 

Fic. 368. Parasitic ascomycetes 
Left, Ustilaginoidea virens, an asco- 
mycete parasitic on rice (Oryza 
sativa) (x 4); right, ergot (Claviceps 
purpurea), an ascomycete parasitic 
onrice (x 3). In both cases the black 
bodies are produced by the fungus 


Fic. 3869. Yeast (Saccharomyces), show- 
ing single cell, budding cells, and the 
formation of ascospores in cells. (x 960) 
the formation of holes in the bread. 
Saccharomyces is a single-celled 
plant. It reproduces by bud- 
ding (Fig. 369). In this process 
a protuberance grows from the 
cell and becomes constricted off, 
thus forming a new individual. 
A daughter cell may begin to. . 
bud before it has been constricted 
from the parent cell, and in this 
way chains or irregular masses of 
cells may be formed. Under cer- 
tain conditions the contents of a 
cell may divide to form four spores 
(Fig. 369). It is on account of this method of spore formation 
that Saccharomyces is included in the Ascomycetes. Its relation 
to the Ascomycetes is, however, doubtful. 
