194 Hhodora [SEPTEMBER 
PERIDERMIUM PYRIFORME AND ITS PROBABLE 
ALTERNATE HOST. 
J. C. ARTHUR. 
EanLv in June of this year I received from Dr. Charles Thom a 
specimen of Peridermium pyriforme Peck, collected near Storrs, 
Conn., on branches of Pinus rigida Mill. This is a species rarely 
seen, only three previous collections being known, and its discovery 
in a locality where it can be under observation and study is a matter 
of interest. The species forms numerous and conspicuous aecia on 
the smaller branches, bursting out through the bark, and showing 
as large white peridia filled with orange spores. The affected branches 
are not much swollen by the fungus, and are usually small, less than 
2.5 cm., rarely up to 5 cm. in diameter. 
So far as known, all species of Peridermium on the bark of pines 
are the aecial stages of corresponding forms of Cronartium. Upon 
the receipt of Dr. Thom’s collection the question of the probable 
telial host presented itself. In the eastern United States only two 
species of Cronartium have so far been recognized: C. Quercus 
(Brond.) Schroet., and C. Comptoniae Arth. In the same general 
region there are also two bark forms of Peridermium on pine: P. 
Cerebrum Peck, and P. pyriforme Peck. It has been proven by means 
of cultures, performed independently by Dr. C. L. Shear and the 
writer, that P. Cerebrum is the aecial stage of C. Quercus, and' it was 
a simple inference that P. pyrijorme doubtless belongs to C. Compto- 
niae. 
While this information was being communicated to Dr. 'Thom, the 
spores which he had sent, and which were not yet dry, were sown on 
Myrica cerijera, a plant of Comptonia in good growing condition not 
being available at the time. No infection was obtained by this sowing. 
This negative result is without much significance, however, as no 
examination was made to see if the spores germinated. 
The next observations on the rust in the ficld were made July 5, 
when Dr. Thom found Comptonia peregrina, growing “all around the 
bases "of the affected pine trees, showing abundance of the characteristic 
uredinia of Cronartium Comploniae. The spores of the Peridermium 
,! See Bull. Torrey Club xxxiii, 420 (1906), where the history of these collections is 
given, 
