282 
Mycologia 
fungus into the stem was by way of the lenticels, and wedges of 
mycelium, using this means of ingress, could be easily made out 
in the bark. 
It should also be mentioned that the piece from which the sec- 
tions were cut was left with its lower end in water, and in a little 
more than a day a vigorous growth of mycelium had developed 
from the cut surface on the diseased portions. (Plate 145, fig. 3.) 
There is therefore no doubt that Hymenochaete agglutinans is 
a facultative parasite. Yet the question at once arises, Why 
should it require two years to kill a small branch like that de- 
scribed above? In this connection we might recall the action of 
Thelepliora laciniata Pers., 2 a fairly close relative of Hymeno- 
chaete. For some time this fungus has been known to kill young 
plants by enveloping them with its mycelium and practically 
smothering them to death. It would appear that in the present 
case also a similar although more local effect of the fungus ob- 
tains. The close band of the fungus surrounding the stem be- 
comes tighter and tighter as the stem grows in diameter, similar 
to the condition so familiar in the case of a vine twining around 
a stem. Moreover, as the fungus increases the area of its opera- 
tions, the original band becomes hard and dry. It is significant 
also that the region where the fungus first encircled the stem is 
actually smaller in diameter than the part above. (Plate 145, fig. 
5.) That this is not due to a thicker growth of the hymenium 
above, was proved by cross sections. 
Such a condition, then, would produce a genuine girdling effect, 
resulting in weaker and weaker growth of the parts above, but 
increased growth of the parts below. Possibly not until the stem 
is thus weakened does the fungus commence its parasitism upon 
the tissues. 
It might be argued that parasitism of the fungus alone could 
produce these symptoms, as indeed really happens in the chestnut 
bark disease. But if this were the case, death should ensue as 
soon as the stem is once girdled by the fungus, or very soon after. 
There is every indication, therefore, that here the parasitism of 
the fungus is supplemented by a mechanical, choking action. 
2 Hartig, R. Der zerschlitzte Warzenpilz, Thelephora laciniata Pers., Unter- 
suchungen aus d. forstbot. Inst. 1880. 
