78 
Vol XXX, No. 1 
Journal oj Agricultural Research 
very early, before a sufficient mass of 
mycelium has been formed to enable 
the pycnia to develop. Either aecia 
or telia might then develop on the 
mycelium as the first spore form fol¬ 
lowing infection, dependent on the 
available food supply or the maturity 
of the tissues. 
It is well to recall at this point that 
the telial sori on stems, sheaths, and 
sepals strongly suggest the normal sit¬ 
uation in microforms, and it is enlight¬ 
ening to review briefly the cytological 
situation which has been found in the 
species of short-cycle Puccinia and 
Uromyces which have thus far been 
studied. 
It is convenient to consider these in 
two groups. In the first the primor- 
dium of the telium is made up of uninu¬ 
cleate hyphae, and the conjugate con¬ 
dition arises as a definite process, by 
cell fusion or nuclear migration, in a 
manner similar to that found in aecia. 
This is the general situation in the 
following species: Puccinia (Nephlyctis) 
transformans Ellis and Ev. investi¬ 
gated by Olive (5), Puccinia ( Polythelis) 
fusca (Pers.) Wint. by Pavolini (7), P. 
malvacearum Bertero by Werth • and 
Ludwigs ( 8 ), P. buxi DC. by Moreau 
(4) and Uromyces scutellatus (Schrank) 
Lev. and Puccinia rossiana (Sacc.) 
Lagh. by Kursanov (3). Uromyces 
laevis Korn., studied by Kursanov, 
probably also belongs in this group, 
but the actual process of the formation 
of the conjugate condition has not 
been observed. 
In the second group the primordium 
of the telium is made up of binucleate 
hyphae and the vegetative mycelium 
is also primarily binucleate. The tran¬ 
sition from a uninucleate to a binucleate 
condition in these forms has unfor¬ 
tunately not been observed, but it is 
assumed by the authors that it occurs 
very early in the vegetative growth of 
the mycelium. This group includes 
Puccinia fergussoni Berk. & Br., P. 
asarina Kze., P. aegopodii (Schum.) 
Mart., Puccinia sp. (P. conferta Diet. & 
Holw.?) on Artemesia, and Uromyces 
gagae Berk, as investigated by Kursa¬ 
nov ( 3) and P. adoxae Fuck, and 
Uromyces scillarum (Grev.) Wint. by 
Blackman and Fraser {2). 
It should be pointed out that, except 
for Puccinia malvacearum, P. buxi , and 
P. rossiana , the species of the first group 
normally develop pycnia; while in 
those of the second group, without 
exception, pycnia are normally absent. 
Uromyces ficariae Wint. is especially 
interesting in this connection. Black¬ 
man and Fraser (2) record that— 
the general mycelium appears to exhibit single 
nuclei, but the mass of mycelial hyphae round 
about the teleutospore sorus as well as those directly 
connected with teliospore formation appear to have 
conjugate nuclei. 
They did not find how or where the 
change took place. Moreau ( 4 ), how¬ 
ever, found all the mycelium uninu¬ 
cleate and the binucleate phase begin¬ 
ning in lower ceils of the telial primor¬ 
dium. Kursanov (3), on the other 
hand, more nearly confirms the find¬ 
ings of Blackman and Fraser (2). He 
finds, however, only a small amount of 
uninucleate hyphae, the vegetative 
mycelium being prevailingly binucleate. 
A more detailed review of the litera¬ 
ture of this subject would show that in 
the first group there was considerable 
variation in the amount of sporophytic 
tissue developed between the origin of 
the binucleate condition and the forma¬ 
tion of teliospores. 
We apparently have, therefore, in 
some forms of short-cycle rusts a very 
short sporophyte, while in others the 
origin of the conjugate condition has 
arisen at varying distances back from 
the mother cell of the teliospores, some¬ 
times only a little way, sometimes far, 
possibly even near to the point of infec¬ 
tion by the gametophytic basidiospore. 
It seems to the writers that this 
cytological situation, especially as found 
in the second group of species men¬ 
tioned above, parallels very closely that 
described for P. podophylli by Olive. 
It is unfortunate that in these short- 
cycle forms the fusions have been ob¬ 
served only in the cases where the 
change takes place at the base of the 
telium. This circumstance, however, 
serves to point out the wealth of prob¬ 
lems awaiting solution in this field, and 
it is hoped that students of cytology will 
soon give us the necessary link to make 
the chain of evidence complete. 
PHYLOGENETIC CONSIDERATIONS 
It is pertinent to ask what is the 
significance of the peculiar life history 
as shown by the Podophyllum rust. 
Without attempting at this time to go 
into the evidence which has determined 
their position, it may be stated that the 
writers of this paper are among those 
who believe that, regardless of what 
the most primitive rust may have been, 
the long-cycle species in the group 
Pucciniaceae at least are the older and 
that the short-cycle forms as exempli¬ 
fied by the microforms of Puccinia and 
Uromyces are derived or reduced forms 
and are relatively more recent. 
It follows, then, that during the 
process of development from a long to 
