BIRCH TREES IN EPPING FOREST AND ELSEWHERE. 281
shaped perithecia with long necks make their appearance, either
in the same or in a separate pustule. Within each perithecium
are numerous asci, each containing eight uniseptate ascospores.
Melanconis stilbostoma, being dimorphic, has been named
many times. In the conidial form it is Melanconium bicolor,
Nees., Melanconium betulinum, Schm, et Kie., Melanconium elevatum,
Cordae, Didymosporium elevatum, Lk., Didymosporium betulinum,
Grev. With spermatia it is Naemaspora aurea, Per., Naemaspora
aurea, Friesio, Libertella betulina. Mazerio. With ascospores it
is Sphaeria stilbostoma, Fr., Valsa stilbostoma, Kicks., Sphaeria
pulchella, Currey. As fungus perfectior, nisi integer, it is
Melanconis stilbostoma, Tul.
From observations made during the summer, the inference
is that Melanconis stilbostoma is the cause of the death of so many
birches, but as far as I have been able to ascertain, there is no
record of this fungus among plant diseases. All the authorities
that I have been able to consult state that it attacks dead
branches only, especially those of Betula alba. Tulasne, however,
does go so far as to mention that it is found on branches still
moist with sap.
Before the supposition that Melanconis stilbostoma is the
cause of the disease can carry any weight, it must be demon-
strated that the fungus occurs also on the living branches, and
for that purpose the selected specimens now exhibited have been
chosen. The branch taken from a tree on Strawberry Hill has
the pustules more crowded than is usual. They had formed
while the cortex was still green, and before the wood showed
any signs of decay. There were no leaves on this tree in the
early summer. It was possibly first attacked last autumn, but
not before the leaf buds and catkins for this year had been
properly formed, and although these buds had not expanded,
they were still green. Another specimen, with the green leaves
still on, shows the fungus in its perfect form. One side only of
the branch is covered with the pustules, and the wood of that
side alone is brown ; it may be noticed that an offshoot from this
branch is still covered with green leaves. This case admits of
two explanations, either the wood died on one side from some
cause not at all evident, and became discoloured, and then the
fungus attacked the dead wood ; or the fungus attacked one side