Jan. 1,1925 
Opmposiie Life History of Puccinia podophylli ScJiw. 67 
am convinced that the aecidia which are borne on 
the sheaths arise, not from gametophytic cell 
fusions, but only from preexisting binucleate 
hyphae; therefore being secondary and sporophytic 
in character, and thus similar in origin to the 
teleutospores. 
He found in the lesions on the leaves 
that a much more abundant uninu¬ 
cleate mycelium is present in the 
younger tissues and that the pycnia 
arise from this mycelium. 
In those older leaves, however, in which the 
aecidia have begun to form their chains of spores, 
binucleate mycelium has become quite prevalent 
in all the sections examined, especially at the bases 
of the aecidial cups. These sporophytic hyphae 
intermingle with the uninucleate mycelium, often 
entering the broad, caeoma like base of tha young 
aecidium, there functioning directly as basal cells 
of the rows of the binucleate aecidiospores. In still 
older stages on leaves, binucleate mycelium appar¬ 
ently prevails by the time the aecidium cups have 
for the most part broken open to discharge their 
spores, * * *. 
His examination of the later telia 
which form from aeciospore infection 
shows that they arise from a localized 
binucleate mycelium. 
In interpreting the results of his ob¬ 
servations he assumes that the uninu¬ 
cleate, or gametophytic mycelium, and 
the binucleate or sporophytic mycelium, 
are independently but simultaneously 
perennial in the plants from which his 
material was taken and that the pycnia 
are the only structure borne on the 
uninucleate mycelium, while both the 
early teliospores and the aecia develop 
from the binucleate mycelium. He 
assumes that basidiospore infection 
would result in a localized mycelium 
on which pycnia and aecia would be 
developed, the expectation being that 
this would be prevailingly uninucleate. 
In connection with a discussion of 
the principle that in perennial rusts the 
gametophytic mycelium in young 
shoots grows more vigorously early in 
the season than the sporophytic, the 
following quotation is of interest: 
The fact that the teleutosori break out very early 
from the tissues of the leaf sheaths, some distance 
below the tip of the stem, and that the binucleate 
mycelium prevails in these sheaths almost to the 
exclusion of the uninucleate hyphae does not, to 
my mind, vitiate the above statement, which ap¬ 
plies only to the younger tissues of the shoot. I 
interpret these facts somewhat as follows: the uni¬ 
nucleate mycelium grows with especial vigor into 
the rapidly expanding tip and young leaves of the 
new shoot, growing somewhat ahead of the lagging 
sporophyte. The latter apparently chooses ordi¬ 
narily the more mature tissues for its most vigorous 
growth and thus early comes to predominate in the 
riper tissues of the poorly nourished leaf sheaths of 
Podophyllum, as well as later in the older leaf 
tissues. 
As a part of Olive’s discussion of the 
probable reason for the development of 
the early telia on the sheaths and later 
the secondary aecia on the leaves from 
the same binucleate mycelium, the fol¬ 
lowing significant statements are found: 
Quite likely the degree of maturity of the tissues 
and the quality of the nourishment supplied to the 
parasite govern largely this phenomenon of the 
early development of the teleutospores, just as these 
factors doubtless determine the cessation of the 
production of the repeating spores and the begin¬ 
ning of the production of the teleutospores in other 
long-cycled rusts. The tissues making up the leaf 
sheaths of young shoots of Podophyllum are un¬ 
doubtedly mature, as well perhaps as poorly nour¬ 
ished, as is shown by the character of the contained 
protoplasm; hence they present conditions at a very 
early stage not met with again until the host gains 
maturity or even old age. 
It is obviously quite impossible to suppose that 
this early teleutosporic stage in Puccinia podophylli 
has arisen in any other way than from hibernating 
sporophytic mycelium, which has grown up with 
the infected buds in the spring. It could not come 
from an early infection since the aecidiospores, 
which we assume to be the only spores from the 
inoculation of which the teleutospores could arise, 
have not yet begun to form. I will have to confess, 
however, that I have not been able to apply 
de Bary’s test to this species and to look for hiber¬ 
nating mycelium in the underground parts. 
CULTURE EXPERIMENTS 
EXPERIMENTS AT ITHACA, N. Y., 
1916-1917 
One of the authors of this paper 
(Whetzel) has had Podophyllum rust 
under observation since about 1906. 
During 1912 he collected and fixed 
much of the material on which Olive’s 
cytological work was based and fur¬ 
nished him without reservation all the 
information gained from the field ob¬ 
servations which ha/d then been made. 
This assistance is freely acknowledged 
by Olive in the paper referred to above. 4 
The elaborate, though entirely or¬ 
thodox, explanation of the situation 
finally made by Olive did not seem to 
Whetzel adequately to explain the phe¬ 
nomena which had been observed in 
the field. On this account it was de¬ 
cided to test the validity of Olive’s 
hypotheses by culture experiments. 
The first of these was conducted at 
Ithaca, N. Y., during 1916 and 1917. 
The plants used for the experiment 
had been brought several years before 
from a patch of Podophyllum in which 
no rust was to be found and were 
planted on a wooded bank in Whetzel’s 
yard far away from any other patches 
of Podophyllum. Since the planting 
was along the path by which he reached 
the road on his way to the office each 
day, he was able to determine by careful 
inspection each year that no rust ever 
appeared either on the bud scales, stems 
or leaves of these plants. In the sum¬ 
mer of 1916 he collected a large quantity 
4 \ detailed manuscript record of these experiments, together with the correspondence which passed be¬ 
tween Prof. Whetzel and Dr. Olive on the Podophyllum rust, is deposited m the library of Cornell Uni¬ 
versity under the title, “Notes on the Life History of Puccinia podophylli, by^H. H. Whetzel. 
