1204 Wisconsin Academy of Sciences, Arts, and Letters. 
view. Once through the outer wall the hyphae grow straight 
across the cell and pierce the inner wall. 
It is difficult to follow this process except at places where the 
conidia are rather scattered. It was very unusual to find more 
than three or four tubes making their entrance in one section 
(Fig. 6) of an infection spot. There seems little doubt, how¬ 
ever, that the successful entrance of even one germ-tube into a 
plant might under favorable conditions be sufficient to smut the 
entire oat head. 
In the material in which the early stages of infection were 
found the conidia usually had 2-3 nuclei; the majority having 
two (Fig. 6). The conidia which had failed to make their way 
in, usually had about the same number and there was no evi¬ 
dence that the successful ones were in any way different so far 
as number of nuclei is concerned. 
A few days later, and about the fifth day after infection, the 
cells of the leaf sheathe will be found to be full of much 
branched, sparingly septate, multinucleated fungus cells. As 
the hyphae make their way through the leaf sheathe they are 
largely intracellular in position but they become almost entirely 
intercellular in their distribution in the young growing plant. 
Young plants fixed and sectioned ten days to two weeks after 
the infection have an abundance of smut mycelium between the 
cells of the first node and of their tip (Fig. 7). Young plants 
sectioned from this time up until pretty close to flowering show 
practically the same conditions as to distribution of the my¬ 
celium ; it being most conspicuous at the nodes and the growing 
tips. There is, as other authors have observed, apparently some 
kind of an equilibrium maintained between the host and its 
parasite. In spite of the numerous hyphae that run all through 
the growing region the normal functions of the oat cells are ap¬ 
parently not interfered with. The cells divide normally in the 
usual mitotic manner (Fig. 9) and the nuclei and cytoplasm 
give no evidence that they are abnormal in any way. 
The hyphae of the smut are scattered throughout the growing 
tip of the young plant with apparently little reference to its 
structure. The growing tip and the base of the leaves show the 
most abundant hyphae (Fig. 7) ; the central parts of the plant 
