PATHOLOGY OF THE JACK PINE. 7 
the selection of nursery sites, with regard to the topography and 
prevailing winds of the region. 
With the exception of Peridermium cerebrum and P. comptoniae, 
few fungi of economic importance attack the living jack pine in 
the drier parts of its range. On the dry pine barrens of the Lake 
States the jack pine reaches its normal age without much defect 
in the wood arising from fungous diseases, although exceptionally 
old trees of 90 years and more frequently show considerable decay. 
In mixture with other species in the more moist regions of its range, 
particularly in parts of northern Minnesota and of Canada, Trametes 
pini (Brot.) Fr. causes considerable heart-rot in trees of 60 years and 
older. In general, however, this fungus is in negligible quantities. 
In close stands jack pine prunes readily during its most rapid growing 
period, forming straight clear stems. The rapid occlusion of the 
branch knots shortens the danger period for infection by wound 
fungi. It is principally due to this fact that some of the most serious 
wood-destroying fungi do not effect an entrance until the tree has 
reached its period of decline. 
Polyporus sclvweinitzii Fr., causing a butt rot, is usually in greater 
abundance than Trametes pini, but the percentage of infected trees, 
even on the more protected soils, is seldom more than 2 to 4 per cent 
of the stand. The jack pine is a deep-rooted species and unless the 
root system comes in contact with a hard stratum of clay and gravel, 
root-destroying fungi are largely a negligible quantity. In this class 
are Fomes annosus Fr. and Armillaria mellea (Vahl.) Quel., which 
very rarely occur on the jack pine. Only a few isolated and unim- 
portant infections have ever been recorded by the writer. 
The jack pine does not suffer any material injury from needle 
fungi. Those that do occur are mostly of a saprophytic nature. 
Lophodermium pinastri Schrad. is found only occasionally. 
On dry soils in open stands the jack pine frequently shows a 
tendency to form witches'-brooms. The terminal shoot, which is 
the part usually affected, develops into a thick-matted broom, pre- 
cluding any further growth in that direction. Trees thus infected 
usually show a rapid falling off in increment, probably dating from 
the time when the influence of the parasite was first felt. Another 
type of broom formation is confined to the lower and older branches 
and has a similar effect on the growth of the host. These brooms are 
probably caused by some perennial fungus. In the absence of any 
fruiting structures the causal organism can not be determined. 
The jack pine in its eastern range is not subject to mistletoe injury. 
Macoun x reports the occurrence of Razoumofskya americana (Nutt.) 
Kuntze, the lodgepole-pine mistletoe, on the jack pine in Canada. 
1 Macoun, John. Catalogue of Canadian Plants, pt. 3, p. 422. Montreal, 1886. 
