Enpotu1a CANKER OF CHESTNUT 583 
Most of the early writers confined their attention to the pycnospores, 
and it has only been within the last few years that attention has been 
called to the fact that the ascospores also are instrumental in the spread 
of the fungus. Murrill (1906 a) suggests the agency of wind, squirrels, 
birds, insects, mice, moles, and rabbits, and later (1906 b) rain—the 
last only carrying the spores from one part of a tree to other parts. 
Hodson (1908:5) says, in regard to the dissemination of the pycnospores: 
“Wind is probably the principal agency, but the spores are no doubt 
carried by animals, birds, insects and by shipment of infected material. 
“The disease spreads locally through the gradual distribution of the 
spores from tree to tree, and at a distance chiefly through the shipment 
of infected material, such as nursery stock, bark, nuts, and other products. 
There is a possibility that long-distance infection is also effected by means 
of migratory birds.” ; 
Metcalf and Collins (1911:9) state: ‘‘ As both kinds of spores appear 
to be sticky, there is no evidence that they are transmitted by wind except 
where they may be washed down into the dust and so blown about with 
the dust. The spores are spread easily through short distances by rain; 
particularly they are washed down from twig infections to the lower 
parts of the tree. There is strong evidence that the spores are spread 
extensively by birds, especially woodpeckers, and there is also excellent 
evidence that they are spread by insects and by various rodents, such 
as squirrels. The disease is carried bodily for considerable distances in 
tan bark and unbarked timber derived from diseased trees. One of the 
most prolific sources of general infection has been the transportation of 
diseased chestnut nursery stock from infected to uninfected localities.” 
One of the writers of this bulletin (Rankin, 1912, a and b) called atten- 
tion to the fact that the ascospores are forcibly ejected into the air, and 
that these can be caught up by the wind and carried for considerable 
distances and may well be responsible for a large part of the infection. 
Fulton (1912:51) reports experiments in which he tried to dislodge spore 
horns by a strong blast from an electric fan. He found that bits of the 
spore horns were sometimes broken off and carried for short distances, 
but were too heavy to be carried for great distances. 
Anderson and Babcock (1913) have considered the problem of dissem- 
ination more in detail than have the other writers. Unless otherwise 
mentioned, the matter considered below is taken from their bulletin. 
Man 
Mutrill (1908 a) was the first to call attention to the danger of spreading 
the disease into new localities on diseased nursery stock. Metcalf and 
Collins (1909:49) gave especial attention to this phase of the matter, 
