NOTES ON THE ANATOMY OF PERIDERMIUM GALLS 1 9 
the broadening of the rays in its members, due to traumatic and other 
stimuH, can not be considered of phylogenetic importance. They 
may be formed to supply some need of the plant, and if such is true 
they are probably physiological rather than phylogenetic in their 
significance. Taken as a whole we know comparatively little about 
the structure of pathological plant tissue, and until more is known it 
is hardly safe to base any very strong conclusions on it phylogenetically. 
The rays are more numerous in the gall than in normal wood, a 
given area of tangential section of the gall having approximately 
twice as many rays present as the same area of normal wood. The 
proportion of ray tissue is greater than this, as the cells are larger as 
a rule and more numerous in the rays of the gall. It might be well 
to mention in this connection that Anderson (2, p. 337) found that 
there were often twice as many rays present in parts of Abies halsamea 
infected with Peridermium elatinum as there were in normal parts. 
The ray tracheids present some interesting peculiarities. In the 
normal wood of the jack pine these are strongly reticulated, in the 
gall the reticulations are often very much reduced or absent entirely. 
The ray tracheids thus combine characters of both hard and soft pines. 
Tracheids sometimes border the rays (center of plate I, figure 4) 
which are similar in many respects to the peculiar tracheids figured 
by Thompson (14) from the rays of the traumatic stem wood, and the 
normal root wood of Pinus resinosa. 
Resin canals are few and widely scattered in the older wood of the 
jack pine but are more numerous in the younger wood near the pith. 
Close associations of canals occur but seldom in either the young or 
old wood. In cross sections of galls the canals may be as much as 
three times as numerous as in the normal wood, varying somewhat in 
different individuals. They are often arranged in concentric rings, 
so closely associated in places that only the rays intervene (plate I, 
figure i). Anderson (i, p. 472) found a similar arrangement in parts 
of Abies infected with Peridermium elatinum. The canals in this gall 
have a lining of living nucleated cells and are evidently not merely 
resin passages such as are described by Maule (11, p. 18) from the 
traumatic wood of certain conifers. A great increase over the normal 
number of resin canals sometimes takes place in traumatic pine wood. 
According to Thomson (16, p. 38) there may be 7-8 times as many as 
normal in the traumatic wood of Pinus resinosa. 
An interesting thing in connection with the distribution of resin 
