A DISEASE OP PISTES CAUSED BY CKONARTIUM PYEIFOEME. 13 
along the column with its growth. The period of teliospore formation 
for each telium is from one to two weeks. The teliospores germinate 
in situ as fast as they mature, without being detached from the telial 
columns. As each teliospore germinates it develops a basidium, 
which when typical bears four sporidia. The sporidia borne on each 
basidium, however, are usually less than four. The sporidia become 
detached as soon as mature and are carried away by even the slightest 
breeze. They readily infect the younger part of pine trees, thus 
completing the life cycle of the fungus. From observation it appears 
probable that germinating sporidia usually gain entrance into the 
tissues of the pines through wounds or in wound callus where young 
cells are exposed. Inoculations with another species, Cronartium 
cerebrum, on pine trees (Pinus virginiana) without wounds have failed, 
while at the same time, other conditions being similar, they were 
successful in wounds. 
Since each generation of uredinia on Comandra plants is followed 
within a few days by one of the telia, there is a continual produc- 
tion of sporidia from the time the telia first appear till the end 
of the growing season. This greatly extends the period of pos- 
sible infection for pines, a period which must be from two to four 
months, depending upon the length of the growing season in pines, 
which varies not only at different altitudes and in different latitudes, 
but also from season to season. 
It is highly probable that the various spore forms of this fungus, 
especially the seciospores from the pines, may be carried about on 
the bodies of birds and of the smaller animals. In this manner they 
could be carried even to greater distances than is possible by wind 
dissemination. 
If young pines in nurseries should become infected, the danger 
of a much wider dissemination of the fungus than has already taken 
place in nature is at once possible, with man as the agent. Under 
conditions such as occur in many localities both in the eastern and the 
western United States it would be easily possible for the pines in 
nurseries to become badly infected, owing to the abundance of Coman- 
dra plants in the vicinity. 
EFFECT OF THE FUNGUS ON ITS HOST PLANTS. 
EFFECT OF THE ^CIAL FORM ON PINES. 
The immediate effect of the fecial form, Peridermium pyrifo'rme, 
varies in different species of pines and on the same species under 
different conditions. When young lodgepole pines or western yellow 
pines are attacked, either on the trunk or limbs, there commonly 
develops a slightly swollen area in the region of the infection. If 
the infected area encircles the trunk, as it usually does, a spindle- 
shaped or fusiform swelling may result (PL II, fig. 3), which varies 
