70 
Journal oj Agricultural Research 
Vol. XXX, No. 1 
Some of these were placed in flats, 
covered with potting soil, and placed 
out of doors with a heavy covering of 
straw. Some were potted at once and 
placed in the greenhouse. The material 
which was placed in flats was brought 
into the greenhouse in March, 1918, 
when the leaves were just emerging 
from the sheaths. No rust developed 
on either set of plants, though they 
were grown to maturity. 
In March, 1918, before the buds had 
swollen to any extent, a second lot of 
rhizomes were dug from a patch which 
was known to have been heavily rusted 
during the previous summer. These 
were thoroughly washed, potted in 
potting soil, and allowed to develop 
in the greenhouse. No sign of rust 
infection appeared on any of them. 
An inspection of the remaining 
plants in the patch of Podophyllum 
from which the last-mentioned rhi- 
zhomes had been dug was made at 
intervals during the spring and sum¬ 
mer of 1918 and the plants were found 
to be heavily infected, showing the 
early development of telia on the 
sheaths and stems, pycnia and aecia 
later on the leaves, and finally the 
late crop of telia on the under side of 
the leaves. 
Stems showing the early telial sori 
and the attached rhizomes were col¬ 
lected in the spring of 1918 and were 
studied in an effort to determine the 
extent of the mycelium. Free-hand 
sections were made, beginning in the 
region of the sori and progressing down 
the stem into the rhizome. The sec¬ 
tions were mounted in chloral hydrate 
and iodine, which furnishes a satis¬ 
factory medium for the study of such 
sections. The mycelium is easily dis¬ 
tinguished by this method and was 
found only in the immediate region of 
the sori. No mycelium was discovered 
lower down in the stem or in the 
rhizome. 
This series of experiments taken in 
conjunction with the one made at 
Ithaca would seem effectively to dis¬ 
pose of the hypothesis put forward by 
Olive that the rust is perennial in the 
buds or rhizomes. 
A number of other experiments were 
considered desirable, however, in order 
to determine as accurately as possible 
just what did occur. The question 
naturally arose as to whether there 
might be some difference in the telio- 
spores formed early in the season on the 
stems and sheaths and those formed 
later from aeciospore infection, either 
in their ability to cause infection or in 
the sequence of resulting spore forms. 
It was also considered desirable to 
conduct some of the experiments with 
somewhat more refined methods and 
under as strict control as is feasible in 
dealing with growing plants and with 
a fungus which can not be grown in 
pure culture. 
Experiment 3.—The telial material 
which was used for the following in¬ 
oculation experiments was obtained in 
the spring and summer of 1917 in the 
same patches of Podophyllum from 
which the rhizomes used in the previous 
experiment were taken. The first 
material was collected May 28, 1917, 
and consisted entirely of sheaths and 
stems bearing the early crop of telia. 
These were placed out of doors on the 
surface of potting soil in flats and left 
till the following spring, 1918. On 
July 17, 1917, material of the late crop 
of telia which develop from aecial in¬ 
fection and occur abundantly scattered 
on the under surface of the leaves was 
collected and handled in the same way 
as the sheath and stem material men¬ 
tioned above. Finally, in the fall of 
1917, after the Podophyllum plants had 
died down and the leaves were more or 
less disintegrated, surface soil from a 
patch of heavily infected Podophyllum 
was collected and placed out of doors 
to winter. At the same time rhizomes 
were again collected from a patch of 
Podophyllum which had shown no in¬ 
fection during the year and were 
placed in flats, covered with potting 
soil, and left out of doors with protec¬ 
tion during the winter. In March, 
1918, these rhizomes were brought into 
the greenhouse, thoroughly washed, and 
potted. Some of the pots were given 
a surface coating of the surface soil 
obtained from the infected Podophyl¬ 
lum patch, some were mulched with the 
soil and stems from the flat prepared in 
May, 1917, and some with the soil and 
leaves from the flat prepared in July, 
1917, as described above. It should be 
pointed out that the sheaths, stems, and 
leaves had largely disintegrated after 
overwintering and most of the telio- 
spores were mixed in the surface soil of 
the flats in which they had been kept; 
hence the reason for using the soil as a 
mulch. As the buds of the potted 
plants developed they pushed up 
through this mulch and became ex¬ 
posed to infection. 
The results of this experiment were 
as follows: In one of the pots mulched 
with soil, sheaths, and stems bearing 
the early teliospores, pycnia and a few 
aecia developed on the leaves of one 
plant and pycnia and aecia together 
with a few telia immediately associated 
with the aecia on another. In the pots 
mulched with soil and leaves bearing 
