} 
Generations , and General Cytology of the Uredineae . 365 
is the essential part of fertilization (as various plants and animal eggs and 
that of Cyclops show) ; the second may take place at the same time as the 
first, or it may be delayed for a time, or, as in the Uredineae, it may be 
delayed until the stage corresponding to chromosome-reduction. 
The fusion-nucleus in the teleutospore undergoes changes which 
correspond to synapsis , and when it divides there is seen to be a reduction 
from the four chromatin masses of the paired nuclei to two chromatin 
masses ; owing to the absence of chromosome-formation in most of the 
nuclear divisions an actual reduction in number of chromosomes cannot be 
observed. The process of fusion and reduction in the teleutospore is 
followed by a definite tetrad division in the c promycelium/ so that the 
teleutospore corresponds exactly with the spore-mother-cell of the higher 
plants, the { promycelial ’ cells being really of the nature of spores. 
As the fusion of the two nuclei is delayed throughout the whole of the 
sporophyte there is associated with the reduction from four to two chromatin 
masses a process of nuclear reduction from two nuclei to one. 
Nuclear division in most of the cells of the Uredineae is of an 
exceedingly simple type. The nuclei (whether single or paired) lose their 
membrane, the nucleolus becomes extruded, and the chromatin condensed 
into one, or sometimes two, masses. A rudimentary spindle can sometimes 
be observed, and upon this the chromatin becomes spread and is drawn 
apart into two or four pear-shaped masses which separate and form 
the daughter-nuclei. In the paired (conjugate) state the nuclei divide 
side by side in close juxtaposition, passing pari passu through the various 
stages of division, as described by earlier observers. 
In the promycelium the two divisions are much more typical. In 
G. clavariaeforme a well-marked spindle with centrosomes and polar radia- 
tions was observed. The first division showed a formation of numerous 
chromosomes, though their behaviour on the spindle is not typical and 
there is doubt as to whether a definite splitting actually occurs. In the 
second division the chromatin forms no chromosomes, but merely a network 
which covers the spindle, and is later drawn apart into two portions. 
The spindle in the case of the second division in the promycelium of 
G. clavariaeforme , and apparently also in the case of the first, is formed free 
in the cytoplasm between the two portions of a divided centrosome (like the 
‘ Centralspindel * of Hermann), and afterwards comes into close relation 
with the nucleus. 
The simple form of division found in the Uredineae is to be considered 
as reduced from the typical method of karyokinesis. 
The two structures observed constantly during nuclear division by 
Sapin-Trouffy and Maire, on which they base their views of chromosome- 
reduction, cannot be considered of the nature of chromosomes, but are 
merely chromatin masses. They probably represent the chromatin derived 
