1216 Wisconsin Academy of Sciences , Arts, and Letters. 
of the spore, the nucleus being pushed to one side by it. It is 
Tather difficult to distinguish the fusion nucleus inside the spore 
as the process of fusion is not complete until the spore has at¬ 
tained a very thick wall. This takes up the stain and makes it > 
difficult to see any structures inside the spore. 
The hyphae are the largest found in any of our common 
smuts. They lie in the intercellular spaces among the palisade 
parenchyma and pulp parenchyma cells of the leaf and form 
long strands across the air spaces above the lower epidermis. 
The branching is characteristic of this smut, and of Urocystis at 
least, if not of other species; a side branch always originating in 
front of a partition across the main hypha (Fig. 49-55). The 
cells are typically binucleated; the two nuclei usually lying in 
the part of the cell formed by the main hypha, although one of 
them may lie out in the branch. 
. The nuclei are large, occupying a large part of the transverse 
diameter of the cell lumen and always lying in its main axis. 
They show a well differentiated nucleole ^and chromatin reticu¬ 
lum (Fig. 51). While conjugate divisions were not observed, 
it seems entirely probable that they occur here as in the rusts 
where the nuclei are frequently similarily placed. In spore 
formation the tubes which lead to the small branch that is to 
form a spore are entirely too small to admit more than one nu¬ 
cleus at a time, and the two may be seen following one after the 
other into the young spore (Fig. 57). It is impossible, of 
•course, at this time to distinguish whether the two going in, are 
sister nuclei, or nuclei that have been produced by conjugate di¬ 
vision from a pair in the main hypha. I have been unable to 
find division figures in the nuclei. 
The large haustoria are especially striking in this species and 
serve probably both as holdfasts and as organs by which the host 
plant is drained of its food. Kaciborski (34) has given a good 
account of their external morphology with the exception of the 
appressorium but did not discuss their nuclei. 
These haustoria originate like ordinary side branches from 
hyphae in the intercellular spaces. They are binucleated and 
usually short (Fig. 49). They are pushed out against the cell 
wall and there begin to branch, not to form a sack as Raciborski 
