[KIRSCH] ORIGIN AND DEVELOPMENT OF RESIN CANALS 75 
sempervirens mentioned above, where the canals are only formed in 
the traumatic wood it is rather peculiar that the tissues forget to ‘re- 
vert’ and ‘sterilize’ the wound until the end of the growing season. 
In addition, it must be borne in mind that a comparatively small 
amount of resin is formed by the young cells, the resin formation being 
exhibited strongly only several years after the appearance of the 
parenchyma cells. 
Frank (7, 75) saw this point, as the following passage will show: 
“From fresh wounds there is a flow of turpentine-like substance, which 
hardens on the surface of the wound. Since, however, all Coniferæ, 
normally exhibit turpentine in certain organs, it is a questionable 
point, if and to what extent resin formation in the region of wounds is 
a pathological character. Obviously, the resin which is poured out 
immediately after wounding, is from the normally occurring resin 
canals.”’ 
Moreover, Jeffrey leaves the following point out of consideration. 
Any resin which escapes from the wood of a tree does so mainly by way 
of the horizontal passages, and since in the majority of cases mentioned 
by him no horizontal canals were present, the contents of the vertical 
canals would have no outlet, and could, therefore, take no part in 
sterilizing any wound at any time. 
Further on, Jeffrey makes the following statement (14, 6): “It is an 
interesting fact that the formation of traumatic resin canals in the 
Abietinæ is most marked in those genera in which the resin canals are 
normally somewhat sparse or entirely absent. In Pinus, where the 
resin ducts of the wood are abundant in both the vertical and hori- 
zontal planes, a marked reaction leading to the formation of tangential 
rows of traumatic ducts seldom or never occurs.” This is most likely 
due to the fact that Pinus is able to handle a larger amount of food by 
means of its parenchymatous tissues than normally presents itself, and 
hence it shows little or no reaction in case of ordinary wounds. That 
in cases of serious injury, however, the formation of the so-called resin 
passages can be greatly exaggerated even in those trees which normally 
contain a very large number of these structures is seen from the follow- 
ing account by Strasburger (33, 529). 
A tree of Pinus silvestris, which is one of the most resinous of the 
pines, was girdled at sixty-two years of age and survived the operation. 
In this case it is obvious that the amount of food available would be 
very much more than in a case of simple wounding, for the food from 
the whole tree would be dammed up at this point. In the three years 
following the girdling abnormally strong growth rings were formed. 
The fourth and fifth year after the girdling afforded rings only half as 
wide as that of the third year. The first annual ring formed above 
