96 EVOLUTION OF PLANTS 
blances indicate any real relationship, and it is quite as 
likely that they are signs of degeneration, the most 
marked resemblance being the absence of division walls 
in the hyphe. On the whole, the smuts seem to be really 
much more nearly related to the rusts. 
We have finally to consider, among the Fungi, the 
peculiar organisms, the yeast-plants, which are the 
principal agents in alcoholic fermentation. They are 
unicellular forms, the individual cells being oval in 
shape and multiplying rapidly by the peculiar mode of 
cell-division known as budding. They may also, 
under special conditions, develop a number of spores by 
internal division. The structure of the cells is ex- 
tremely simple, and the presence of a definite nucleus is 
still open to question. 
The relation of the yeast-fungi to the other members of 
the group is still a matter of controversy. Some authori- 
ties consider them to be very low organisms, having 
some affinity with the bacteria; others, on the strength of 
their forming spores internally, somewhat like the Asco- 
mycetes, regard them as the lowest members of this 
group; still others have thought that they represent a 
permanent conidial stage of forms related to the smuts, 
as in the latter the spores under certain conditions may 
bud much as do the yeast-cells: that is, the yeast- 
cells are supposed to be spores arrested in their devel- 
opment so that they never form filaments or hyphe. 
Which of these hypotheses is the correct one, must at 
present be left unanswered. 
