PATHOLOGICAL FORMATIONS. 
The morphological and anatomico-physiological relations of 
the organs formed in the normal vital processes of plants having 
been considered so far as they relate to our purpose, some other 
phenomena may still be mentioned which are produced by dis- 
turbances of the normal] processes. 
When a part of a plant is wounded by the human hand or by 
an animal, it is capable of repairing the injury. The most 
usual form of protection is the formation of cork (protective 
cork) on the wounded place. Figure 109 a shows, for example, 
how on a fruit of the Vanilla, which has been wounded by an 
insect, cork has been produced around the wounded place, 
whereby access of air is excluded from the inner tissues. Cork» 
is the ordinary form of protection for delicate organs, but 
naturally, is only met with in such places where cells occur 
which are still delicate and readily suberized. If, on the con- 
trary, the stem of a dicotyledonous woody plant is wounded 
down to the wood, the plant selects another means of protec- 
tion, since cells here become exposed which can no longer be- 
come suberized. Accordingly, in all the cells of the wood 
which border on the wounded place, gum (wound-gum) is pro- 
duced as an exudation of the thick membranes, which gradually 
fills the cell cavity and thus directly closes the wound. The 
masses of gum and resin which occur in the dead heart-wood of 
the officinal woods ( page 260) are probably such protective gum. 
During this process, in those portions of the bark which are 
still capable of development, the plant endeavors to close the 
_ wound from both sides. There are thus produced, by very 
—_— = in the _—— cambial zone, om, inflated 
