NOTES ON THE ANATOMY OF PERIDERMIUM GALLS 
13 
infiltration of substances from the layers of wood further out. The 
galls examined in this respect were of various sizes, some large, others 
small. More especially were the rather small ones on larger branches 
examined as these seemed most likely to show an exception if such 
were true. None of them did, however, so it seems likely that the 
infection usually if not always takes place during the first year's 
growth of the branch which bears the gall. This, however, is not true 
for all species of Peridermium, as Hartig (8, p. 173) describes an 
Text-figure i. Gall of Peridermium cerebrum on Pinus Banksiana. a, 
external view of the gall, h, median longitudinal section of gall. (Both figures about 
natural size.) 
instance in which a pine was attacked by P. Fini in the fifteenth year 
of its growth. According to Anderson (2, p. 311) P. elatinum seldom 
attacks branches of Ahies halsamea over five years old, while Ahies 
pectinata, according to de Bary (4, p. 257), is attacked both on young 
and old parts, and a case is reported where a stem a foot thick and 
having 60-70 rings of growth was infected. 
A median longitudinal section through one of the larger galls 
