ARTHUR: PROBLEMS IN THE Stupy OF PLantT Rusts 17 
should not mislead us into thinking that the family represents a 
reduced branch of the Basidiomycetes, for in all probability one 
family is as highly developed as the other, only one is along sapro- 
phytic lines of adaptation, and the other along parasitic. There 
are, in fact, some reasons for supposing that the Uredineae stand 
in the lead. 
Of the various problems which cytological studies are expected 
to illuminate, none is more pressing than to discover the probable 
original function of the spermogonium. This body was at first 
held to be of the nature of the male sexual organ, hence the name, 
but all the studies and observations of recent times have done little 
to establish this view. Most students of the rusts ignore the 
structure entirely, or attach slight importance to it. 
Without going into an argument, or even presenting opposing 
views, permit me to call attention to some significant facts regarding 
the spermogonium. These facts, it seems to me, tend to substan- 
tiate the assumption that we are dealing with the structure that 
originally functioned as the male reproductive body, but which 
long since in the developmental history, has ceased its functional 
activity, and become in all respects a disappearing organ. In the 
first place, in all cases where the life-cycle is known, the first body 
that is formed from the mycelium arising from teleutosporic conidia 
is the spermogonium. It begins the series of spore structures. 
In a full series the next structure is the aecidium, then comes the 
uredo and the amphispore if the latter occurs at all, both being 
asexual spores to meet requirements for rapid and certain distribu- 
tion, and finally the teleutospore, having its characteristic mode of 
germination. The uredo and amphispores may be left out of this 
cycle, and often are, without disturbing the vigor and success of 
the organism. If the aecidium is omitted, however, the spore- 
form immediately associated with the spermogonia will be the 
uredo. These uredospores which arise along with spermogonia, 
however, differ in some physiological characteristics from those 
that arise later, having a greater disturbing influence upon the host, 
and are usually designated as primary uredo. It is significant in 
this connection that cytologically the aecidiospore and the uredo- 
spore are essentially alike. Going a step further, in what I con- 
sider reduction, and having both the aecidium and uredo omitted, 
