Holden a?id Harper—Nuclear Phenomena. 75 
cell receiving one of the daughter nuclei. The division of the 
daughter nuclei is followed by further cell division. The 
teleutospore has grown into a four celled promycelium, each cell 
of which contains a single nucleus. From each of these divis¬ 
ions a sterigma arises on the end of which is produced a sporid- 
ium and a pro mycelial nucleus passes out into each sporidium. 
The sporidium is then unincleated but its nucleus divides. 
This nuclear division is not followed by cell division and there 
is thus constituted a binucleated sporidium. This is the first 
hinucleated cell of the new generation. Starting with the 
sporidiumj there is developed a mycelium of binucleated cells, 
which divide by conjugate division. From the teleutospore to 
the sporidium we find uninucleated cells. From the sporidium 
to the teleutospore we have binucleated cells. 
The regular presence of two and only two nuclei in the my¬ 
celial cells of the rusts presents a very unique condition among 
plants. Coenocytic cells contain numerous nuclei but there is 
much evidence that the nuclei of the binucleated cells of the 
rust bear a very different relation to each other than do the nu¬ 
clei of multinucleated cells. Strasburger (8) has described nu¬ 
clear and cell division in such typical coenocytic cells as those 
of Cladophora. The nuclei in these cells may amount to a 
hundred or more in number. Nuclear division takes place by 
the ordinary karyokinetic process. The division of the nuclei 
is not necessarily simultaneous. Nuclei in various phases of 
division as well as even resting nuclei occur in the same cell at 
the same time. There seems to be no close time relation bet- 
tween the division of one nucleus and that of its neigh¬ 
bor. Later the cell divides. There seems to be no direct and 
constant relation between nuclear division and cell division. 
With the conjugate nuclei the division is always simultane¬ 
ous and conjugate nuclear division is always followed by cell 
division. The fusion of the conjugate nuclei in the teleuto¬ 
spore is then something different than a fusion between any two 
nuclei of a coenocyte. Whether it is to« be interpreted as 
equivalent to a typical sexual fusion is a very interesting ques¬ 
tion, 
As we have seen the two nuclei which fuse in the teleutospore 
can be traced back in separate series through binuclated cells 
