1. 1) BRANCH - The branch wounds expose all tissues, from the new outer tissues to that of the older tissues in the center of the tree. (fig. 46)
2. 2) OUTER CORE - The outer core wounds usually expose only the most recently formed tissue. This depends, of course, on the depth of the wound. (fig. 47)

Figure 46 Branch wound	Figure 47 Outer core wound

When microorganisms infect, they grow from compartment to compartment. The column of discolored or decayed wood that is seen macroscopically will be a composite of many columns as seen in these radial sections through drill wounds. (fig. 48)

In a vertical plane, each growth ring ("tree") will have its own column of discolored and decayed wood. The response of the "older trees" or innermost rings is slower and weaker than that of the "younger trees." (fig. 49)

The "holding strength" of Wall 1 decreases as the injury goes inward. The older "trees" have a weaker response. This action determines the shape of the column, shown here from a radial view.(fig. 50) In a sense, the wounds set the staqe. The DISCOLORATION PROCESSES begin immediately after wounding when the tree reacts-both by chemical reaction and by plugging. When the pioneer microorganisms invade, the discoloration processes may intensify. The DECAY PROCESSES begin when microorganisms begin to digest cell walls. Many factors affect the rate of the discoloration and decay processes-severity of the wound, position, size, time of year of wounding, wounding agents that import materials into the wound, and the types of microorganisms that infect.

Figure 48
Figure 49

Figure 50

A branch wound will usually have this shape of column. Of course, there are many variations to this shape.(fig.51)		Ring rot is one configuration associated with branch infections.(fig.52)
	Figure 51		Figure 52

Figure 53 Echinodontium tinctorium

When many branches die at about the same time, the entire central column of the trunk may be decayed. The diameter of the column will be the diameter of the tree when the branches died. Although the death of the branches determines the diameter of the internal column, the fungi associated with the decay in the column may have entered the branch and trunk after a long growth period in the dying branch. Some fungi, such as Echinodontium tinctorium and possibly Fomes pini and others, first infect minute branchlet stubs on the living branch and therefore usually do not infect the large, freshly exposed branch stubs. (fig. 53)

Branches are often decayed by a wide variety of microorganisms that do not enter the trunk. Branch decay of this type is very beneficial as the tree is pruned when the branches fall. (fig. 54)

Figure 54

Figure 55

Also, concentrations of pigments and oxidized protective materials will usually be greater along the side of the column closest to the cambium. The column stays to the pith side of Wall 4. (fig. 55)