236 
Journal of Agricultural Research 
VoL XXV, No. S 
blackberry characters, were inoculated with aeeidiospores from a wild 
“yellow” (black) raspberry May 18, 1921. On July 19 many sori were 
found on the leaves of young canes of one of them. No sori could be 
found on other plants of the same variety near by. During the spring 
of 1922 these experiments were repeated more satisfactorily in the green¬ 
house. Several wild blackberries were planted on a bench. After they 
had grown out vigorously they were inoculated on several different days 
with aeeidiospores from black raspberries. Spores were rubbed and 
sprayed on the underside of young and of old leaves, and infected rasp¬ 
berries bearing aecidia were placed under the same infection tent. Thus 
the blackberry leaves were frequently covered with spores, and condi¬ 
tions were certainly made favorable for infection. At no time later 
during the summer could telia be found on any of the leaves, old or 
young, although leaves of the black raspberry plants which had been set 
in the same infection tents, as noted, were later covered with sori, and 
they had not been especially inoculated. Four root shoots from these 
plants were systemically infected with the short-cycled rust in 1922. 
Such results might be interpreted to indicate that biologic races occur 
and that the blackberry is immune to the long-cycled rust from the black 
raspberry, but of course it would first be necessary to prove this particular 
species or variety of blackberry to be susceptible to infection by the 
sporophytic stage of the long-cycled rust from other blackberries. Six 
Kittatinny blackberries were sprayed on May 29, 1922, with aecidio- 
spores from the black raspberry and six others with aeeidiospores from a 
wild blackberry found at Upper Marlboro, Md. On July 19 a few teleuto 
sori appeared on leaves of each set, and on August 2 other leaves were 
found well infected with the rust from both sources, suggesting that the 
Kittatinny variety is susceptible to infection by the long-cycled rust 
regardless of whether the rust comes from the black raspberry or from 
this wild blackberry. 
It will require much work to settle definitely the question of biologic 
races of the orange-rusts owing to the difficulties encountered in sys- 
temichlly infecting a susceptible plant with the gametophytic stage. 
The difficulties can not be overcome nor the questions answered by work¬ 
ing with the telial stage alone, because a plant might be susceptible to 
infection by the telial stage of a certain strain but not be to its orange- 
rust stage or vice versa . The long-cycled rust occurs on blackberries, 
dewberries, and black raspberries. Can teleutospores be obtained with 
equal readiness on the dewberry by sowing sporidia from teleutospores 
obtained from each of the three types of hosts? In spite of the evidence 
of his preliminary experiments, the writer can not believe that the answer 
to each question will be in the affirmative. 
During the fall of 1920, Mr. George Darrow had some plants of Rubus 
canadensis , the mountain blackberry, sent from Phillips, Me., to Bell, 
Md., for breeding experiments. They were planted in a plot adjacent 
to several cultivated varieties. In May 1921, these plants appeared to 
be seriously affected with the long-cycled orange-rust. During July 
and August large numbers of teleuto sori were found on the leaves of these 
mountain blackberries and spores were not rare on the leaves of the 
Ward, Joy, Mercereau, and the loganberry, showing that in the vicinity 
of Washington, D. C., the sporophytic stage spreads naturally from the 
mountain blackberry to several of our well-known varieties of other 
species. There are at Arlington Farm, Va., some loganberries adjacent 
to a wild dewberry originally obtained from Phillips, Me., when in an 
