DRIEPER ARTICLES. 
A GALL UPON A MUSHROOM. 
WHILE collecting fungi in one of the gorges in the neighborhood 
of Ithaca, September 12, 1902, I found two specimens of the common 
Omphatia campanella atfected by a gall insect. Every fungus collector 
is familiar enough with the destruction of his choicest mushrooms by 
insect larvae, but in every case that has been recorded, so far as I can 
determine, the effect of insect attacks has been exclusively destructive. 
However completely the fungus may be riddled by larvae, there is ordi- 
narily no growth-response whatever on the part of the plant. 
y) 
Omphalia campanelia Batch. 
G. I.— Half of pileus affected by gall insect, showing normal gills and gall 
viewed from belo 
Fic. 2. ee viewed my the side. 
Fic. 3. — Same showing the appearance of the vertical secti 
Fic. 4. oi etell section see the path of the larva mre ie gall. 
Here we have a very different condition of affairs, as the accom- 
panying figures will show. The normal pileus of O. campanella is very 
thin, in fact less than 1™" in thickness, and with gills attached the 
entire structure is inside 3™", as a rule. Here, in contrast, we have 
a white mass, homogeneous in section, about 8" in radial diameter, 
6™" in thickness, and some 12-15™™ in length. Around the ends of 
the gall, where it adjoins the normal tissue, the even under-surface is 
broken, as represented in figs. and 3, the folds and wrinkles repre- 
senting gills whose original nature becomes more evident as they 
approach the normal tissue. The effect upon the upper surface is 
shown by fig. 2. In this the gall causes a marked enlargement, 
deforming that half of the pileus. The two galls were much alike 
1903] 223 
