CANKER GROWTH ON ABIES BALSAMEA 31 
number of annual rings of the wood a cavity or pocket is thus 
formed at the dead spot. Often several such cavities are formed 
when the cambium has been killed at more than one spot. All 
these cavities or pockets are always filled with hardened resin, 
forming one or more resin-pockets or “ resin-galls,”’ * 
These resin-pockets are formed at first between the bark and 
wood where the cambium has been killed, but they are later enclosed 
in the wood by the formation of new annual rings of wood (fig. 7). 
The normal wood of Aédzes balsamea does not contain any resin 
canals, but in wounded and hypertrophied wood, such organs are 
not infrequently formed. The writer has already called attention 
to the occurrence of pathogenic resin-canals in the tumors formed 
by Aecidium elatinum, when affecting the branches of Adies bal- 
Samea, t 
The wood of the canker invariably contains pathogenic resin- 
canals, which are similar to those formed in tumors caused by the 
Aecidium (fig. ro). The canals are all vertical ones, no horizon- 
tal canals are formed. The canals vary in diameter from 25 to 85 u 
and in length from a few millimeters to 2-4 centimeters. They 
do not extend through the whole length of an internode or year's 
growth, like the normal resin-canals of Pivus and Picea. In the 
wood of Adies the canals are formed in groups or chains on one 
side of an annual ring and usually in the spring wood (figs. 7 and 
8). Usually only one chain or ring of canals is formed each year, 
but sometimes two are formed in the same ring, one in the spring 
and one in the fall-wood zone. Not infrequently, a chain of canals 
is formed in the fall at the end of the growing season and another 
one the following spring in the new wood (fg. 8). In this case, 
it seems that the abnormal resin secretion, necessitating the for- 
mation of the canals, begins in the late fall or summer, when it is 
Not completed, but continues the following spring. A new set of 
canals are now formed at the cambium, the canals formed in the 
fall having in the meantime become thick-walled and their resin 
contents hardened. 
*It appears that resin-pockets would be a better term than ‘‘resin-galls’’ 
(‘* Harzgallen *’) with which to designate the solid masses of resin which are not in- 
frequently found in the wood of the Abietineae, since the term gall conveys the idea of 
4 visible hypertrophied living part of a plant organ caused mainly by insects and fungi. 
t Bot. Gazette, 24: 337- 
