6 
BULLETIN 212, U. S. DEPARTMENT OE AGEICULTUEE. 
species of Quercus x should be of much significance in control work. 
Quercus velutina and Q. coccinea are two scrub oaks frequently form- 
ing a conspicuous part of the jack-pine type, particularly in Michigan. 
Methods could be devised for the eradication of these worthless 
species, thus removing the alternate host of the fungus. However 
impracticable this may be on a large scale, hi wood lots and small 
holdings this would not be a very "difficult 
matter. The removal of infected branches of 
young growth could be done in the orchard- 
like stands of jack pine on the more sandy 
soils, thus saving many young trees from early 
suppression. 
In a few instances, hi the region studied, 
young jack pine was found to be diseased by 
Peridermium comptoniae (Arthur) Orton and 
Adams (Cronartium comptoniae Arthur). 
(Fig. 4.) In the experience of the writer this 
fungus was not common. The secial stage of 
the fungus is chiefly characterized by a slight 
fusiform swelling, seldom forming the spheri- 
cal galls so characteristic for P. cerebrum. The 
peridia rupture with a sharply serrate or 
spiny margin. The fungus is further dis- 
tinguished from P. cerebrum by attacking 
principally young seedlings (PL I, fig. 3) and 
causing excessive brooming of the branches. 
It was not found on more mature growth. 
P. cerebrum attacks both young and old trees. 
P. comptoniae has its alternate stage on sweet 
fern 2 ( Comptonia peregrina and Myrica gale) . 
Without the production of the teliospores on 
these plants the fungus can not reproduce 
itself on the jack pine. 
As a precaution agains tthese Peridermiums 
entering the forest nursery and the possibility 
of their transportation to other regions, all 
alternate hosts, such as species of oaks and 
sweet ferns, should be removed from the 
vicinity of the nursery. This immunity zone 
should be extended as far back from the nursery as time and means 
will allow. Before new nurseries are established a pathological sur- 
vey of the immediate region should be made as to the presence of 
these hetercecious pine rusts. Much attention should also be given 
Fig. 4. — Young jack pine infected 
■with Peridermium comptoniae. 
Note the ruptured peridia with 
their serrate margins. 
1 Demonstrated by Dr. C L. Shear, Jour. Myc, vol. 12, p. 89, 1906. 
• Demonstrated by G. P. Clinton, Conn. Agr. Exp. Sta. Rent., 1907, pp. 380-383, 1908. 
