20 
ALBAN STEWART 
canals in this gall is the fact that there is no increase in the number 
in the uninfected parts above the gall. Anderson (i, p. 473) states 
that the parts of Pinus Strohus above infections of Agaricus meleus 
contain more resin canals than do normal branches. He also reports 
the presence of resin canals in the branches of Abies which are above 
infections of Peridermium elatinum. A similar condition is mentioned 
by Mer (12, p. 367) in Abies, above infections of Plioma ahietinae. 
We have in this instance a rather striking correlation between the 
effects produced by two species of the same fungus. In one case 
the fungus is unable to exert an influence on the structure of the host 
beyond where it is actually present in the tissues of the same, in the 
other case it is far reaching in its effects, and is not only able to modify 
the tissue of the host some distance from the parts infected, but is also 
able to stimulate the productions of organs that are not normally 
present there. 
Summary 
The more important facts presented in this article are briefly 
summarized below: 
1. Both an alternate and an opposite arrangement of bordered 
pits in the radial walls of the tracheids. 
2. An unequal thickening of the walls and luminae of the tracheids. 
3. Very short tracheids with blunt end walls, which resemble 
parenchyma cells except in the pitting. 
4. Cells which are transitional between tracheids and parenchyma 
cells in the pitting. 
5. The presence of true wood parenchyma cells. 
6. A small production of thin-walled summer tracheids. 
7. A probable absence of bars of Sanio from many of the tracheids. 
8. An increase in the number of rays in the gall wood. 
9. A tendency towards the production of multiseriate rays. 
10. Ray tracheids which are transitional between those of both 
hard and soft pines. 
11. The presence of a balled or whorled arrangement of tracheids 
in tangential section. 
12. A great increase in the number of resin canals in the gall 
wood but no such increase in the uninfected wood close by. The 
examination of this gall has revealed so many points of anatomical 
interest that a further study of this subject seems to be worth while. 
