1224 Wisconsin Academy of Sciences, Arts, and Letters . 
alone were produced, the penetrating hypha being a further de¬ 
velopment or a better adaptation to the life of the fungus. The 
mildews may have developed their haustoria in a similar man¬ 
ner. 
The term, spore ball, is quite loosely used to include a variety 
of aggregations of spores. In general all that seems to be meant 
by the term is that a number of spores hang together for a 
longer or a shorter period, the question of their common origin 
not coming into consideration further than that they all or¬ 
iginated in the same region. In Sphacelotheca all that the 
word, spore-ball, implies is that the spores which come from the 
breaking up of the hyphae in a certain region, and are formed 
in a similar way to those of Ustilago, remain clinging together 
after formation. In Doassansia Alismatis it is only the side 
buds from the tangle of hyphae in an intercellular space which 
form the spores of the ball, the fertile ones being on the inside 
and the sterile layer on the outside. In D. deformans the ori¬ 
gin of the spores is probably the same but the relation of sterile 
and fertile cells is exactly reversed, the sterile cells in this 
species being on the inside and a single layer of fertile ones on 
the outside. In Urocystis the spore ball is a very definite 
structure composed of closely related cells all originating from 
one of the hyphal branches. 
It is easy to see, of course, that the spore-ball originated as a 
group of spores, of more or less common origin, clinging to¬ 
gether. It is a more difficult physiological problem, however, 
to discover how it should be that in one species, the sterile cells 
all lie at the interior of the ball, while in another species un¬ 
doubtedly of the same genus they only form a single layer on 
the outside of it. I shall not attempt at present an explanation 
of the origin of these different types of spore-balls nor propose 
a new system of naming for the different varieties. The neces¬ 
sity for work in this line is, however, conspicuous and it is evi¬ 
dent that we are at the present time including under the name 
of spore-balls a variety of structures that are not at all homolo¬ 
gous in their origin. 
In my opinion the results of my studies seem to indicate that 
the two divisions of the smut group may be more distantly re- 
