ioo8 
Journal of Agricultural Research 
Vol. V, No. 33 
zation from the oriental species, would be susceptible to infection. It is 
not known whether this species is capable of infecting the apple. No 
records of its occurrence on that host have come to our attention. 
While the only telial host known for either species is the Oriental 
juniper, it should be noted that this species is a very variable form, of 
which many varieties are recognized, and is closely related to several 
American species of the Sabina group. It is not at all impossible that 
either of the rusts under discussion might find a congenial host among 
some of the American species of Juniperus and become firmly estab¬ 
lished in this way. 
The infection experiments of the writer with Gymnosporangium koreaense 
have shown that it develops very vigorously on the quince. Since the 
species of Gymnosporangium which are known to infect the quince do not 
usually develop so vigorously on that host as on others, the vigorous 
growth of this species on the quince may be an indication that G. koreaense 
is rather cosmopolitan in its habits and in a new habitat finally may prove 
capable of infecting a wide range of pomaceous hosts. 
Several of the forms of Juniperus chinensis are commonly planted for 
ornament in various parts of the country, and practically all of these 
are imported directly from Japan. Both Gymnosporangium photiniae 
and G. koreaense are apparently common in Japan and, as shown by the 
American records, are liable to be frequently introduced on the telial 
host. If infected trees should be planted in the immediate vicinity of 
pomaceous hosts capable of harboring the aecial stage, it is possible for 
either species to become established, as has occurred in Oregon. In the 
case of the outbreak of G. koreaense in the nursery at Oakland, Cal., it 
is probable that the junipers which were the source of infection for the 
rust on the pears have been sold and distributed, and the rust may 
already be established in one or more localities that have not yet come 
to the attention of plant pathologists. 
In the case of Gymnosporangium photiniae it is uncertain whether the 
telial stage is perennial or biennial. Clinton (i) records that an infected 
tree planted in the greenhouse developed after two years a new sorus in 
a different part of the stem than the point of original infection. It is 
known that several other related species which cause fusiform enlarge¬ 
ments of the stem are perennial and take more than one season for the 
development of the telia after infection. As in all species of Gymno¬ 
sporangium, the infection of the telial host occurs in the summer, and the 
mature sori do not develop till the following spring or, in some species, 
until the second spring after infection. G. koreaense , so far as known, 
is an annual form, requiring a new infection of the telial host each year. 
In the case of either species it would be difficult to detect the presence 
of infection during the summer or dormant season, making inspection at 
the port of entry difficult. To be certain that infected junipers were 
