Studies in the genus Gymnosporangium—ll, Report on cultures 
made in 1915 and 1916 
B. O. DopGE 
(WITH PLATE 8) 
The writer (2) reported the infection of Chamaecyparis with 
Roestelia transformans, and later (3) gave an account of experi- 
ments which resulted in the infection of the red cedar with G. 
clavipes, G. macropus, G. globosum and G. nidus-avis. . Arthur’s 
results (1) were confirmed in the case of G. clavipes, and it was 
stated that the other species required nearly two years to mature. 
G. globosum as well as G. macropus may develop strictly foliicolous 
galls. In 1917 the writer reported the infection of Chamaecyparis 
with G. Ellisiit (4). Weimer (12) states that G. clavipes matures 
in two years, although it seems he was unable to make the infec- 
tions. He also reports the development of one small gall of G. 
macropus on cedars which he had previously inoculated. The 
abstract of the writer’s paper read at a meeting of the Botanical 
Society of America, 1916, has not appeared in print, and as further 
work has resulted in the accumulation of considerable data, a 
summary of the cultures of 1915 and 1916 is presented at this time. 
GYMNOSPORANGIUM CLAVIPES 
A red cedar eight inches high obtained from Cold Spring 
Harbor, Long Island, in May, 1915, had at the time a few sori of 
G. clavipes on the stem. This material was used to infect Crataegus 
oxyacantha. 
Six red cedars were sprayed with aecidiospores August I, 1915, 
and left in the infection frame two days. Several other cedars 
were growing in the same greenhouse, otherwise no controls were 
provided. TasLe I includes all cedars that were growing in the 
greenhouse at the time aecidiospores were being shed from the 
rust on the Crataegus. 
The results shown in the table indicate that spores may mature 
the first spring after inoculation, although in some cases they do 
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