1222 Wisconsin Academy of Sciences, Arts, and Letters. 
In the yeasts since in some cases ascospores are produced af¬ 
ter the fusion it has been assumed by Guilliermond that it cor¬ 
responds to the nuclear fusion that occurs in the ascus, forming 
what he considers a zygospore. In the ascus, however, the nu¬ 
clear fusion is not the direct sequence of a cell fusion, there be¬ 
ing only one cell fusion occurring in the Ascomycetes, and that 
is between an oogonium and antheridium at the origin of the as- 
cocarp. Therefore it would seem more natural to assume that we 
have in the yeasts of this type where fusions occur before spore 
formation a shortened life cycle with the formation of a single 
ascus bearing ascospores inside it. 
In the smuts, however, the case is different. It is probable that 
at the present time the parasitic mycelium rarely or never starts 
from the conjugated conidi a or promycelial cells even though 
they represent the old sexual form of conjugation. It is quite 
possible that this normal sexual fertilization has ceased to play 
any essential role in the life cycle of the smut even though it 
recurs regularly when the promycelial cells or conidia are 
brought under certain conditions which favor it. Functionally, 
though not morphologically, it may have been replaced by the 
intracellular nuclear fusions of the chiamydospore, preceded by 
a longer or shorter series of conjugate divisions. As Harper 
(28) has noted, the same process may be going on in certain As¬ 
comycetes. A true fertilization between the oogonium and an¬ 
theridium has been found by Harper (20) in Pyronema and the 
Mildews. In others of this same group these structures seem to 
be wanting or are rudimentary. In the smuts the morphologi¬ 
cal equivalents of the oogone and antherid are the fused conidial 
or promycelial cells. Functionally the fusion of the cells is no 
longer of much importance in the life cycle of the smut but they 
still represent the primitive gametes. In the Basidiomycetes 
cell fusion has disappeared entirely but in the smuts it is re¬ 
tained in a rudimentary state and is only functional in a lim¬ 
ited fashion under certain conditions. 
It seems probable also that there may be different degrees in 
which this fusion occurs in the different species of smuts. In 
Hstilago Tragopogi according to Federly (15), the nuclei of the 
fused conidia travel toward each other and apparently fuse as a 
