207 
lying there, while those free of the fungus began to decay in a few 
days. Under a summer apple tree also, the antiseptic influence of 
the fungus seemed evident, for ‘not only were apples, which were 
lying in the grass and covered with the fungus, preserved for 
weeks, but when a portion only of the apple was affected, that 
part withstood decay longer than the remainder of it. Hallier has 
explained the matter in a fairly satisfactory way, judging by the 
statement of Frank * who approves of the explanation, by supposing 
that the fungus does not permit yeast or similar things to gain access 
to that part of the fruit. 
Observations directly bearing on this point were made as follows: 
September 26, an apple still hanging to the tree was fully envel- 
oped with the fruiting tufts of Oidium, the tissues of the apple 
throughout being a uniform light brown. The outside was removed 
to make herbarium specimens, and in twenty-four hours it was again 
covered with a growth of spores. The apple had a pleasant fra- 
grance, and tasted sweet, like good dried apple. There was not the 
least mustiness or disagreeable quality It compressed between the 
fingers in the same way as moist dried apple, and pulled apart with 
like tenacity. Under the microscope no foreign substance but the 
mycelium of the Oidium could be detected, and there was a total 
absence of all bacteria and yeast. In the spring previous a similar 
observation had been made on a Rhode Island Greening apple taken 
from the cellar. It bore a small, brown discoloration on one side 
and was laid on the table to await examination. In the mean time 
it gradually turned brown throughout, and exhaled a very agreeable 
odor. After a time black specks appeared on its surface, which 
proved to be the spore perithecia of Spheropsis malorum Berk., a 
fungus not known to have close relationship with the Oidium. The 
texture and qualities of the apple when cut open did not differ materi- 
ally from that described above, it only being of a somewhat deeper 
brown color. Again no bacteria or yeast were present. In both 
cases the apples after being cut were exposed to the air of the room 
for days without decay setting in. 
Without entering upon further observations, the generalization 
may be ventured, that in many cases the higher fungi do not of 
themselves produce the kind of decomposition known as rot or decay; 
to accomplish this they must be aided by bacteria or similar agents 
of fermentation. Doubtless such destructive Species as the Peronos- 
pore of potato rot and lettuce rot, are not the direct cause of the 
offensive putrefaction, but it is due to the bacteria associated with 
them. We very properly hold the higher fungus accountable for the 
result, however, for it first produces by its growth those chemical 
products upon which the bacteria are able to thrive. The products 
of the bacteria in turn, which in some cases are as harmful to higher 
fungi as to the tissues of a flowering plant, do not in these instances 
check the growth of the fungus, but rather contribute to its main- 
tenance and activity. It is a true commensalism, each promoting 
the welfare of the other. The inability of the usual putrefactive 
bacteria to overcome the resistance of the living cells, and_ start 
decay, has been well illustrated by numerous experiments performed 
*Krankheiten der Pflanzen, p. 615. 
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