NOTES ON THE ANATOMY OF PERIDERMIUM GALLS. I 
Alban Stewart 
Peridermmm (Aecidium) cerebrum Pk. on Pinus Banksiana Lamb. 
Peridermium cerebrum parasitizes fourteen species of North 
American pines according to Arthur and Kern (3, pp. 134-135). 
Owing to the wide range of these species the distribution of the fungus 
is also wide, occurring nearly throughout the United States, southward 
to central Mexico, and northward along the mountains to southern 
Alaska according to the above named authors. The jack pine, 
Pinus Banksiana, is one of the species infected by this parasite, large 
woody galls resulting on the branches from its attack. A number of 
these galls came into my possession some time ago, and as a pre- 
liminary examination revealed some rather interesting anatomical 
peculiarities, I thought the material to be worthy of a more careful 
study. The results of this are given in the following pages. 
The galls examined vary considerably in size and age but they 
all occur on rather young branches. The largest one examined has a 
cross diameter of 4.7 cm. and the smallest one a similar diameter of 
about I cm. They usually occur singly but two may sometimes be 
closely associated and later joined together. The outer surface is 
much roughened due to the scaling off of the outer bark (text-fig. la), 
a character which is seemingly more pronounced when spores are 
being discharged than at other times of the year. 
The woody portion of the gall is sharply set off from the normal 
wood above, below, and inside by the difference in color. The normal 
wood is light in color, while that of the gall is distinctly brown, prob- 
ably due to accumulations of resin and other substances in it. This 
brown coloration is usually more pronounced towards the center, 
sometimes the outer layers being free from it. In such cases alburnum 
and duramen portions are well differentiated. Without exception all 
galls examined show a deep coloration into the first ring of growth at 
some point or points in the circumference, and tissue abnormalities 
accompany it. Evidently the fungus was present when this wood was 
formed and the brown color is not due, at least not entirely, to an 
