Nuclear Divisions in the Rusts. 
339 
two conjugating cells of Triphragmimn. In all these cases, one of the con- 
jugants lies below the other, either immediately or else obliquely below. 
But, as has been intimated above, the evidence is not at all conclusive that 
in any case the two cells are derived from the same hypha. In fact, 
wherever positive evidence is present, it points out that the two cells are 
entirely distinct, and are not related as granddaughter cells of the same 
hypha, as Blackman thinks may be the case sometimes. 
In Fig. 30 the partially absorbed partition wall between the two gametes 
appears to be peculiarly bent and contorted. The two nuclei now lie close 
together, and the fusion cell shows evidence of considerable growth. In 
Fig. 31 fusion has apparently just taken place, and the prophases of nuclear 
division have already begun. The sterile cell in this figure is particularly 
interesting. It has swollen up to an unusual size ; further, the process of 
degeneration appears to have left but little of the cytoplasmic and nuclear 
contents, other than the more resistant nucleole. 
Fig. Oyi proves conclusively the statement made above, that the karyo- 
kinetic processes begin at once, on the very initiation of cell fusion, and 
some time before the gamete nuclei come to lie close together ; since the 
migrating nucleus has cast out and left behind in the lower gamete its 
nucleole. As will be seen later, this throwing out of the nucleole is one of 
the first indications of mitosis. 
Figs. 33 and 34 show conditions of particular interest, the significance 
of which will be discussed later, since in both instances nuclei from a lower 
cell are apparently migrating into an upper cell. Fig. 33 is from Tri- 
phragmium , while Fig. 34 is from a preparation of Gymnoconia interstitialis. 
These figures are both quite comparable to Blackman’s Figs. 66 and 68. In 
neither of my figures, however, is there such a tiny pore present as must be 
assumed to be the case in Blackman’s Figs. 67, 69, and 70, where the 
migrating nuclei are drawn out to narrow threads in the process. Figs. 33 
and 34 simply represent cases in which the fusion of the two cells is initiated 
by the beginning of the passage of the protoplast through a very small pore. 
In Fig. 33 the nucleus has just begun to pass through from the lower into the 
upper cell. Both gametes are obviously from distinct hyphae in this 
instance, as are also those of Fig. 34. In the latter figure, fully half of the 
long, stretched-out nucleus has passed through the narrow opening into 
the upper cell, and now partially overlies the nucleus of the upper cell. 
Figs. 35 and 36 represent also cell fusions in Gymnoconia ; both are of 
a similar type, in that the fusion occurs between two cells placed adjacent 
and parallel. These figures recall Christman’s (’ 05 ) Fig. 5, in which one 
gamete lies slightly higher than the other. It is a highly interesting fact, 
and one which will call for comment later, that Figs. 34 and 36 are drawn 
from the same section, and are situated only a short distance from each 
other in the preparation. Here appears to be an instance in which 
