Generations , and General Cytology of the Uredineae. 351 
same mass of cytoplasm and during division , nuclear reduction [fusion), and 
chromosome-reduction. These processes may either take place together 
or be separated by a considerable number of divisions. In the case of the 
higher plants the first two processes usually take place together, i. e. the 
sexual nuclei fuse in the resting state directly they meet 1 . In many 
animal eggs, and a few plants, the second process is somewhat delayed, 
and there is no nuclear fusion until the end of the first division. 
In the case of the egg of Cyclops we have a further stage, for nuclear 
reduction is put off for many cell-divisions, each of the cells showing two 
nuclei which are, however, closely associated together during division. 
In the Uredineae there is a still further stage of separation, for in this case 
nuclear reduction (or fusion) is put off until the stage corresponding with 
chromosome-reduction (vide infra), so, like that process, it is confined to 
the reproductive cells (teleutospores = spore-mother- cells) which are to carry 
on the life-history. The two nuclei, also, instead of dividing together on the 
same spindle divide on separate (rudimentary) spindles side by side. 
Fertilization is, of course, a somewhat ill-defined term, and from a strict 
morphological point of view it is perhaps arbitrary to confine it to any one 
of the three processes just described, for sooner or later all of them must 
occur in the complete sexual cycle. A cell is, however, usually considered 
to be ‘ fertilized ’ directly the stimulus has been given to development and the 
number of chromosomes doubled by the entry of the male cell or nucleus, 
and for such a use of the term fertilization it is obvious that the essential 
point is the first stage — nuclear association in the same mass of cytoplasm 
and during division. 
The time at which nuclear reduction (fusion) takes place is seen from 
the stages given above to be quite unimportant, but, like chromosome- 
reduction, it must occur sooner or later in the sexual cycle. The view 
which would consider fertilization as incomplete until nuclear fusion had 
taken place could hardly be accepted, as chromosome-reduction might 
equally be considered as the end of the process. It would also tend to 
divorce the morphological and physiological aspects of fertilization, for in 
Cyclops and Phragmidium , for example, we should have to consider the female 
cell as developing under the stimulus of fertilization, but with the process 
still incomplete. Besides, all recent work at present tends to show that 
nuclear fusion is mainly a nominal process (hence the term nuclear reduction 
is preferable), a mere change from association within the same cytoplasm to 
association within the same nuclear membrane. 
The view of Dangeard and Sapin-Trouffy, which would consider the 
fusion in the teleutospore as itself a sexual process, was based on an 
1 It is generally believed that in many of the Thallophyta where there is no alternation of 
generations the three processes all take place together, chromosome-reduction occurring before the 
fusion-nucleus divides. 
