340° BOTANICAL GAZETTE [NOVEMBER 
above the tumor. The distribution and number of resin canals 
are given in tables V and VI. 
Resin canals are never found in the healthy part of the 
branch below the tumor. They first appear in sections made 
at the base of the tumor and here only in the outer annual 
rings. All the resin canals of the tumor have their endings 
at the base, between the healthy and the diseased wood. 
The ends are pointed and gradually disappear between four 
tracheids, which in their meristematic condition probably func- 
tioned as epithelial cells. In sections made above the base of 
the tumor, the number of annual rings affected as well as the 
number of canals increases. The greatest number is found in 
the middle of the tumor (table V, section VI), where the canals, 
also reach their greatest diameter. From the middle of the 
tumor toward its apex the number of canals decreases, the 
greater number of them ending at its upper end. Many of the 
canals continue in the affected branches for some distance. The 
affected branches of some witch brooms have no canals (table 
VI, A., sections IV to VIII.) 
Usually, however, with the increase in age of the branch, 
there is a corresponding increase in the number of its canals. With 
the increase in age of the witch broom the outer annual rings of 
the tumor and branches become narrower, often having only a 
few layers of tracheids. With this decrease in width of the 
annual rings, there is a corresponding decrease in the number of 
canals formed in the tumor; but an increase occurs in the num~ 
ber of canals formed in the branches (table V, sections Vi and 
XII to XIV). 
_ The resin canals are usually found in the spring wood, where 
they form a ring of canals separated only by~the medullary 
rays (fig. 14). This ring of canals sometimes extends the 
whole distance around the annual ring. Usually, however, It 
extends only one-fourth to one-half of the distance, with here 
_ and there an isolated canal. Rings of canals and isolated : 
canals are often found in the summer and fall wood. The 
regulatory tissue, or so-called “red wood,” formed of ue oe 
