146 
placed under belljars with one end of the twig in water were then 
infected and the growth of the fungus watched, as preliminary to 
field infections. These latter were made on a number of young 
chestnut trees.in the propagating houses of the Garden as soon as 
growth commenced in the spring, experiments with dormant trees 
being carefully avoided. As the preliminary experiments had led 
me to expect, the actively growing fungus, when transferred 
from bean stems to the branches of the young trees, attacked them 
with vigor and soon caused their death by girdling. 
The progress of the disease in infections through natural 
causes was observed in young trees transferred from the nursery 
of the Zoélogical Park and numerous older infected trees through- 
out Bronx Park. In all of these the fungus was found exceed- 
ingly active at the beginning of the season of growth, before the 
opening buds were able to use the large quantity of nourishment 
at hand. 
The fungus works beneath the cortex in the layers of inner 
bark and cambium. Its presence is first indicated by the death 
of the cortex and the change of its color to a pale brown, resemb- 
ling that of a dead leaf. Later the fruiting pustules push up 
through the lenticels and give the bark a rough, warty appear- 
ance ; and from these numerous yellowish-brown pustules mil- 
lions of minute summer spores emerge from day to day in elon- 
gated reddish-brown masses, to be disseminated by the wind and 
other agencies, such as insects, birds, squirrels, etc. In late 
autumn the winter spores are formed, which are disseminated 
from the dead branches the following spring. 
When grown in artificial cultures, the mycelium of the fun- 
gus is at first pure white, changing to yellow with age, and the 
fruiting ‘pustules are a beautiful yellow. Winter spores sown 
November 27 on agar and transferred to bean. stems showed 
young pustules on December 8 and mature spores in process of 
discharge by December 17. Cultures transferred to sterilized 
chestnut twigs developed with equal rapidity, while those remain- 
ing on agar were considerably slower. Mycelium inserted be- 
neath the bark of living chestnut twigs on December 1 3 devel- 
oped a prominent spore-mass by December 27. Inoculations 
