Aug. 4, 1933 
Systemic Infections of Rubus with Orange-Rusts 
237 
infected condition. On June 24, 1921, leaves of one of the loganberries 
whose vines intermingled with those of the infected dewberry, bore large 
numbers of teleutospores. Another loganberry was inoculated May 23 
with aecidiospores from this dewberry. On July 21, teleuto sori were 
found on several leaves of the loganberry. One of these loganberries 
had also become naturally infected with the “ Kunkelia.” It will be 
interesting to learn whether this variety is susceptible to the gameto- 
phytic as well as to the sporophytic stage of the Gymnoconia. It does 
not follow that a species or horticultural variety is susceptible to the 
orange-rust stage simply because its leaves can be made to mature 
teleutospores. Such an example of close heteroecism has not as yet been 
described, although it may occur. Several plants of the Iceberg variety 
of blackberry were inoculated with sporidia from aecidiospores from the 
wild dewberry. Although shoots chosen for this work were in the best 
condition for infection at the time, no positive results were obtained. 
This variety is very susceptible to the rust from other blackberries, and 
probably is not altogether resistant to dewberry rust. More work will 
be necessary to prove this point. 
SUSCEPTIBLE VARIETIES 
Plants of different varieties of blackberries and raspberries have been 
inoculated with aecidiospores of the Gymnoconia without obtaining 
teleutospores. Some of these failures have been due undoubtedly to 
faulty technic rather than to the immunity of the host to the sporophytic 
stage of the long-cycled rust. The Lucretia dewberry certainly ap¬ 
proaches complete immunity in North Carolina. The writer has never seen 
orange-rust on this variety, although no attempts were made in the first 
experimental work to infect it. Inoculations of the Iceberg, Crystal 
White, Kittatinny, Mercereau, Blowers, Ancient Briton, and the Cran¬ 
dall with the short-cycled form resulted in such success that the failure 
to infect a variety of blackberry received from a nursery under the name 
of “Lawton” suggests that this form, whatever may be its true name, is 
probably immune to the short-cycled rust. This variety formed so many 
root shoots in April, 1921, that it was especially chosen for infection 
experiments without anything being known about its susceptibility. 
Seven separate experiments in which about 30 shoots were inoculated 
in various ways were carried out. Since the conditions for infection were 
fully as favorable as were those which resulted in such marked success 
with the Kittatinny plants which grew near this “Lawton” variety, it 
certainly must be very resistant. Several plants of the McDonald were 
inoculated in the open, but no infectiofa resulted. The attempts to 
infect the “Lawton” were repeated in 1922 with still greater care but 
no infections were obtained. The Snyder blackberry also proved to be 
very resistant. The Taylor, Blowers, and Ancient Briton inoculated at 
the same time were easily infected. 
Fifty separate sowings of sporidia were made on root shoots of culti¬ 
vated varieties of blackberries in nature in 1921. From 1 to 10 shoots 
in each case were covered by the infection chamber, so on an average 3 
or 4 shoots were inoculated each time. Every attempt to infect the 
variety, Lawton, as noted above, resulted in failure. Only one plant 
of the “Eldorado” variety was infected although a number of shoots 
were sprayed with sporidia. The Eldorado is said to be resistant. At 
least one shoot of the varieties mentioned was infected in each of the 
