140 MISSOURI BOTANICAL GARDEN BULLETIN 
are orange-colored or brown. In the course of time the 
branch or tree is girdled, resulting in the death of all parts 
above the canker. If the entire tree above ground is killed, 
numerous sprouts or “suckers” may be produced at its base, 
but these in turn fall a rapid prey to the attacks of the 
parasite. 
Two kinds of reproductive bodies, or spores, are formed by 
the fungus. One of these makes itself evident after warm 
rains in the form of long, thread-like masses called spore 
horns, containing many millions of spores which ooze out 
from small openings in the diseased tissues. The second 
type of spore, the ascospore, is forcibly ejected into the air 
from small orange or brown cushions at the surface of the 
canker. New infections may arise from a number of causes. 
Spores which are washed down the trunk of the tree may 
lodge in a wound and, if conditions are favorable, germinate 
and give rise to a new canker. Spores are also transported 
from one tree to another by such agencies as the wind, birds, 
and insects. The shipment of diseased nursery stock, or of 
unpeeled, diseased logs, or of diseased bark to tanneries, is 
also responsible for the origin of new centers of infection, 
which are frequently at considerable distances from the main 
area of the disease. 
The display of chestnut blight material, obtained from 
Pennsylvania, shows some of the more characteristic aspects 
of the disease, particularly various stages in its development. 
Following is a list of the various specimens on exhibit: 
Young, orange-colored cankers, a month or six weeks old, 
on chestnut twigs. 
A series of specimens showing the gradual increase in size 
and the successive stages in the development of the cankers 
from the young lesions to the last stages on the trunk of a 
forest tree. 
Specimen from which the diseased bark has been torn 
off by the wind, leaving the wood uninjured but exposed. 
Section of a 5-inch tree with a large canker. Trees of all 
sizes, whether in the forest or the orchard, are killed in the 
course of a few seasons. 
Cankers showing characteristic hypertrophy, or swelling of 
the tissues; also others showing characteristic atrophy, or 
shrinking of the tissues. 
Cankers showing both kinds of reproductive bodies: the 
thread-like spore horns and the brown cushions from which 
the ascospores are forcibly ejected. 
“ros cluster of sprouts, or “suckers,” badly diseased at their 
. 
