ENDOTHIA CANKER OF CHESTNUT 581 
if a film of water is present, the walls begin to gelatinize. Undoubtedly, 
as more and more asci are pushed out, some arise in the water to the 
surface and may even project above the surface, due to the disturbance. 
It might be expected, then, that the increased pressure on the ascus wall 
due to the swelling of the contents, at a time when the wall is gelatinizing, 
will result in the sudden rupture of the wall when the ascus arises to or 
above the surface of the water. Since the lower part of the ascus wall is 
the thinner and gelatinizes first, freeing the spores, and since no change 
suggesting pore or other type of apical dehiscence has been found, it is 
presumed that what proves to be a successful method of ejection is due 
merely to a combination of physical factors, not to any structural arrange- 
ments. 
Saprophytic growth . 
Endothia parasitica may live indefinitely as a saprophyte, In this 
condition it is not so restricted in its feeding habits as is the case other- 
wise. Where it is found growing on trees outside the genus Castanea, 
it usually exists there only as a saprophyte. It may be grown in pure 
culture on sterilized twigs of almost any of the common forest trees. 
It has also been grown on a wide range of culture media. Anderson 
and Babcock (1913) report cases in which trees with scattered cankers 
were cut and were left lying on the ground during the summer; in the 
autumn the fungus was found to cover the entire trunk. Also, they found 
that the fungus spreads rapidly in fire-killed bark. When it grows in 
dead bark, no canker-like area is formed, and also the mycelium does not 
progress by the production of fan-like mats but by single threads. The 
fungus spreads through dead bark many times more rapidly than through 
living tissue. Anderson and Babcock made successful inoculations on dead 
bark with ascospores and with mycelium, and on dead leaves and dead 
burs with ascospores. The fungus grew and produced pycnidia on all of 
these. Collins (1913) also found the fungus growing saprophytically on burs. 
Apparently its growth is checked only by failure of the moisture supply. 
In order to determine how long the mycelium lives on logs after they 
have been cut, both with the bark on and with it removed, and also on 
the stumps from which the logs are cut, and whether the fruiting stages 
are produced under these conditions, the following experiment was per- 
formed: Thirty-two trees, some entirely dead and some still living, 
were felled, cut into seven-foot logs, and allowed to remain lying on the 
ground. Some were peeled, others were left with the bark attached. 
Also some of the stumps were peeled. Isolations were made from the 
interior of the bark and the wood — care being taken to avoid getting 
any spores of the fungus in the cultures — during each month for one 
