1905] 1 CHRISTMAN—SEXUAL REPRODUCTION IN RUSTS 269 
granular material, and the whole cell dwindles in size. The chromatin 
of the nucleus seems never to have passed into the resting condition, 
but lies in dense masses, apparently as it was left on reaching the poles 
of the spindle in the nuclear division preceding. The whole nucleus 
is very small compared with the nucleus of the larger cell beneath 
and contains little space between the chromatin masses. The 
material of the nucleus begins to disorganize and soon becomes a 
homogeneous mass, which stains a hazy red with the triple stain. 
The cell beneath this terminal cell, on the other hand, begins to 
enlarge, bulging at the middle, and becomes irregularly barrel- 
shaped. The cytoplasm is dense with small vacuoles. The nucleus 
enlarges greatly and the chromatin matter is distributed through 
its interior, forming a ragged network. There is a large, well-defined 
nucleole. 
We have thus a series of oblong cells standing vertically side by 
side but not much crowded. If we study a series from the margin 
of a sorus to its center, we find gradually more advanced stages, so 
that very many conditions of development may often be found in a 
single section. 
Up to this time in the history, the writer’s observations agree very 
closely with those of BLACKMAN. The subsequent behavior of the 
larger cells, however, which BLACKMAN terms the fertile cells, is very 
different. Many times two can be found which incline toward each 
other, coming in contact in a region on their adjacent walls. At this 
period the remains of the degenerating sterile cells may often still be 
seen (fig. 4). At the point of contact an opening is formed by solu- 
tion of the cell wall and thus the protoplasts are brought into contact. 
The pore is small at first, leaving the bases of the gametes quite inde- © 
pendent, and often the two tips of the gametes are also separate, as is 
indicated by the notch at the apex of the conjugated cells (fig. 5). 
By gradual enlargement of the pore the upper halves of the proto- 
Plasts of the gametes unite to form a continuous cell mass which still 
shows plainly the two distinct bases (fig. 6). The nuclei, which 
before fusion occupied a central position in the fertile cells, now come 
to lie in their upper portions, consequently the two nuclei are brought 
side by side in the conjugated region. Simultaneous division now 
takes place. . Two spindles are formed which lie side by side in about 
