1046 
Journal of Agricultural Research 
Vol. XXVIII, No JO 
an albino variety, was evident later when plants of the Mercereau variety simi¬ 
larly infected also failed to show spermogonia. Infected plants of both varieties 
were observed again the following year to see if spermogonia might not develop 
the second year after infection. At no time in the past three years has the rust 
on these plants produced spermogonia. This fact was the more interesting be¬ 
cause on those plants of the Ancient Briton and Eldorado varieties which had 
been infected with the short-cycled rust in one of the experiments, spermogonia 
had always preceded the aecidia. The rust on a Taylor blackberry which was 
infected when received from the nursery, developed both spermogonia and aecidia, 
but the rust on other plants of this variety which later were artificially in¬ 
fected did not develop spermogonia. 
During the spring of 1923, two root shoots of the Iceberg variety were inocu¬ 
lated with orange-rust, the one was infected by sowing sporidia from aecidiospores 
of the strain from the Ancient Briton which had developed spermogonia, the 
other Iceberg was infected with spores from rust on wild blackberry. Both plants 
inoculated became systemically infected and developed aecidia in 1924. The 
first plant showed many spermogonia on the leaves from the basal shoots as soon 
as they developed; the infected basal shoots from the other plant developed only 
aecidia, no spermogonia. While endeavoring to account for the occasional 
suppression of the spermogonial stage of the short-cycled orange-rust, it was 
discovered that aecidiospores of those strains of the rust omitting the spermo¬ 
gonial stage are uninucleated. Cell fusions do not regularly take place in the 
aecidium primordium. The uninucleated spores develop promycelia when they 
germinate but the promycelia are 2-celled, and each cell produces only one 
sporidium. 
As the figures to be discussed later show, the number of cells in a promycelium 
is not constant for any strain. Promycelia are reported as 2-celled, or 4-celled, 
when one sees large numbers that are 2-celled or 4-celled,’ as the case may be. 
If no spermogonia could be distinguished with a hand lens on an infected leaf 
it would be reported as without spermogonia, when a more careful examination 
with a higher-powered microscope might prove that poorly developed or vestigial 
spermogonia were present. In the discussion which follows, the statement as 
to absence of spermogonia should be read with this understanding. 
The absence of spermogonia may seem to be a point particularly stressed in 
the following account, when it is clear that the facts regarding the production of 
2-celled promycelia which function is the feature which is being set forth as a 
new departure from the regular order of promycelia in the rusts. It will be 
shown later, however, that both of these features are merely the outward expres¬ 
sion of something of relatively far greater significance fundamentally, and that 
is, that an aecidium of the orange-rust of Rubus may arise without cell fusions 
and that the spores matured without such cell fusions are generally uninucleated. 
Since the long-cycled, as well as the short-cycled orange-rusts, have both been 
proved to be widely distributed in America on a number of species of Rubus, 
further evidence on the mere question of their distribution in the form of exten¬ 
sive tables showing germination tests is unnecessary, except as some new element 
enters the discussion. The discovery of uninucleated strains with 2-celled 
promycelia makes it highly desirable that further germination tests be made in 
such a way as to record the different types of promycelia as correlated with the 
relative abundance of spermogonia, as well as the size, form, and color of the 
spores. The abundance of the strain which develops 2-celled promycelia may 
be judged from the following accounts of collections gathered at random in 
various localities in one season. 
