JOURNAL OF AMLTtlRAL RESEARCH 
DEPARTMENT OF AGRICULTURE 
Vol. V Washington, D. C., February 28, 1916 Np. 22 
AN ASIATIC SPECIES OF GYMNOSPORANGIUM ESTAB¬ 
LISHED IN OREGON 1 
By H. S. Jackson, 
Chief in Botany , Agricultural Experiment Station of Purdue University , Indiana 
INTRODUCTION 
Early in June, 1914, specimens of a species of Roestelia on Japanese 
pear leaves were sent to the writer from the office of the Secretary of the 
Oregon State Board of Horticulture. These had been collected in the 
yard of a Japanese family at Orient, in the vicinity of Portland, Oreg. 
The writer visited the locality on June 11,1914, and found two Japanese 
pear trees (Pyrus sinensis) the foliage of which was seriously affected with 
the fungus (PI. LXXVIII, fig. 1). Since all species of Roestelia, so far as 
known, are the aecial stages of species of Gymnosporangium, and none 
are known to be perennial, it was at once recognized that the source of 
infection must be in the immediate vicinity. A search was made for a 
possible telial stage, but no positive evidence of the occurrence of such 
was obtained at that time, on account of the lateness of the season, 
though several varieties of Juniperus, as well as other members of the 
Juniperaceae, were found growing in the same yard, all of which were 
stated by the owners to have been directly imported from Japan several 
years before. Inquiry revealed that the rust had been present in small 
amount the previous season. 
Careful examination showed that the rust should properly be referred 
to Roestelia koreaensis P. Henn., which was originally described from 
material collected in Korea (Chosen), but has since been reported as 
occurring commonly in Japan. An examination of the literature showed 
that considerable confusion has existed regarding the identity and rela¬ 
tionship of certain of the Asiatic species of Gymnosporangium. Twospecies 
This paper is based on studies which were conducted in the laboratory of the Department of Botany 
and Plant Pathology of the Oregon Agricultural College Experiment Station. It is essentially as read at 
the summer meeting of the American PhytopathologicalSociety, at Berkeley, Cal., on August 5,1915, with 
certain additional information obtained from the examination of material in the herbarium of Dr. J. C. 
Arthur, to whom grateful acknowledgment is due for this privilege as well as for helpful suggestions. 
See abstracts in Phytopathology, v. 5, no. 5. P- 293. 1915. and Science, n. s., v. 42, no. 1086, p. 582, 1915. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
ck 
(1003) 
Vol. V, No. 22 
Peb. 28, 1916 
Ind.—2 
