72 THE ROYAL SOCIETYOF CANADA 
is even more commonly present in the case of wounds. This is especially 
the case with large exposed wounds on the aérial portions of the stem 
where there is much necrosis and drying out of the woody tissue. In 
smaller wounds, however, where there is not too great an exposure of the 
ligneous cylinder to dessication, the formation of traumatic resin pas- 
sages described above is very common.” This shows that the common 
idea that the traumatic resin canals are initiated for the secretion of a 
large amount of resin to seal up the wound is rather erroneous, for in 
this particular case, where the largest number of resin passages would 
be necessary they are either absent or very scarce, while they are well 
developed where there is less need for them. The reason for this appear- 
ance is as follows: In the case of large wounds on the aerial portion of the 
tree, the only salvation for it is to build up very rapidly, or at least as 
rapidly as in normal growth, the xylem tissues, and in order to do this 
it has to be able to take full advantage of the abnormal food supply. 
The medullary rays alone are probably not capable of handling this fluid 
rapidly and in such a way as to distribute it uniformly, and hence a 
large amount of wood parenchyma which conducts the food in a vertical 
direction is formed. In the case of small wounds the divisions in the 
parenchyma cells would not be as rapid or as numerous as in the case of 
large wounds, and hence the tensions in the surrounding tissues would 
suffice to form intercellular spaces. In the large wounds, however, the 
division and growth of the parenchyma cells would keep pace with the 
extension of the surrounding tissues, and thus form few if any schizo- 
genous cavities. 
The formation of parenchyma aggregates without a contained canal 
is often seen even in the pines, wherever very vigorous growth is ex- 
hibited. In Pinus chihuahuana this phenomenon is frequently encount- 
ered. 
Another point of interest which Jeffrey observed in Sequoia gigantea 
is the formation of traumatic canals in the phloem (18, 447). This is 
not at all strange, as the possibility of canal formation in the secondary 
growth of a Conifer is co-extensive with the occurrence of the medullary 
rays. 
In connection with Abies balsamea, the following passage illustrates 
several steps in the formation of resin passages. In speaking of a 
wounded root, Jeffrey (13, 448) says, “There is a considerable formation 
of resinous tissue along the inner margins of the last annual ring on both 
sides of the wound, which takes the form of resin cells. Further away 
from the wounded portion, on the left, (13, Fig. 22, plate 70), the 
resinous tissue gives place to a tangential row of resin ducts continuous 
through almost half the circumference of the root, and passing on the 
right into a narrow zone of resin cells, which are in turn continuous with 
