The Uredinece. 
of which are always uninucleate. The stage of the rust resulting 
from infection by these spores is always characterized by the 
production of aecidial spores and spermogonia. These cells are 
produced therefore from a uninucleate mycelium, as first pointed 
out by Sapin-Trouffy. 
The structure of the spermatia causes little difficulty as they 
are single uninucleated cells. Their function however has not been 
clearly understood and as it does not enter into the life-history it 
will be discussed later. The secidiospores however, are not so 
simple in their origin and the nature of the aecidium must be given 
in more detail. The secidiospores are formed from a mycelium, the 
cells of which are uninucleated, but the jecidiospores are developed 
as conidia from a large basal cell which has commonly been spoken 
of as a basidium. The basidium is binucleated and is the first 
cell of the binucleated generation. Its origin will be given in detail 
in another connection. The two nuclei of the basidium divide by 
conjugate or simultaneous division and after the daughter nuclei 
have moved apart cell-division follows, cutting off a cell at the top, 
the aecidiospore mother-cell. The nuclei move apart in such a way 
that the two nuclei in each resulting cell are never sisters. Imme¬ 
diately following this division the nuclei of the ascidiospore mother¬ 
cell divide more apart and cell-division follows, cutting off a very 
small cell at the lower end, known as the intercalary cell. This 
soon loses its identity and the aecidiospore rounds up and is free. 
These binucleated spores give rise to the generation of the rust 
characterized by having binucleated cells. A division of one of 
these cells is always preceded by a simultaneous division of the two 
nuclei and the daughter nuclei which pass to the new cell are never 
sisters. From this generation of the rust the uredospores and 
teleutospores are produced. 
The uredospores are simple. They are either formed singly on 
stalks (Blackman, Fig. 78) or in chains (Harper and Holden, Fig. 2), 
and are always binucleate. They continue this generation of the 
rust as they always give rise to the mycelium having binucleated 
cells. 
The teleutospore history is far more complex, a young teleuto- 
spore is composed of one or more binucleated cells, but these nuclei 
unlike those in the other spores approach each other and eventu¬ 
ally fuse, giving rise to a single large primary fusion nucleus. The 
mature teleutospore marks then the close of the binucleated 
generation and the beginning of the uninucleated. The entire 
life history dropping into two hemicycles. 
