1196 Wisconsin Academy of Sciences , Arts, and Letters. 
regards the fusion as purely cytoplasmic “that leads to a growth 
in the size of the fused cells, perhaps also making them more re¬ 
sistant to unfavorable conditions.” 
Maire (30) in a short note on the spore formation of Tilletia 
Tritici states that not only the spore hut also the mycelial hypha 
from which it arises is binucleated. The nuclei in the spore 
fuse before its maturity. 
Istvanffi (25) thought the conidia of Ustilago Zeae contained 
three nuclei; one in the middle and one at either end. Maire 
was able to show, however, that Istvanffi had mistaken accumu¬ 
lations of cyplasm in the two ends for nuclei and that the spores 
were really uninucleated. 
Federly (15) working on the fusion of the conidia in Ustilago 
Tragopogi finds that a nuclear fusion occurs also. The nucleus 
passes through the connecting tube from one conidium over to 
the nucleus of the other one of the conjugating pair and the two 
fuse. The fusion of the conidia involving thus both nuclear 
and cytoplasmic unions is regarded as a true sexual act and 
Federly opposes the view of De Bary and Harper that it is only 
a vegetative union. 
The rusts are now by many believed to be nearly related to 
the smuts and they present so many similarities to them, that in 
any discussion of the cytology of the smuts a consideration of 
the important work that has recently been done on the rusts is 
essential. 
It was observed by Bosen (35) in 1892 that the rust spores 
were all binucleated and that the so-called “basidium” from 
which the aecidiospores arose was uninucleate. He did not ob¬ 
serve the fusion of the two nuclei in the teleutospore but be¬ 
lieved that it occurred, as he saw them lying closely pressed to¬ 
gether. 
In 1896 Seppin-Trouffy’s (36) general work on the histologi¬ 
cal structure of about 35 species from 10 genera of rusts ap¬ 
peared. In this he was able to show that the two nuclei fuse in 
the teleutospore, and that the mycelium that produces uredos- 
pores and teleutospores is binucleated. He was able to observe 
too that the mycelium was not binucleated at all stages but that 
it originated as uninucleated and later became binucleated. 
