Bob's quote: "Ramshorn (Ram's Horn) which is the curling in of the wall of the tree generally into an opening."
You call it Ramshorn..........I know it by the term 'callus roll'.
The tissue around a cavity opening will callus and form woundwood, particularly along the vertical edges. Woundwood extends in a smooth, thin layer over a firm wound or fill surface, but it rolls inward on itself in a cavity and can become quite thick. If the cavity is large, a callus roll may provide needed mechanical strength to the trunk. The tissue rolls due to a lack of inner surface stability. The callus tissue forms in a thin layer on the inner wood of the tree, but once in contact with the cavity it soon can no longer support itself and begins 'rolling' inward. The more the tissue rolls the more area the roll is able to cover in the attempt to close off the opening to outside alien entities. The callus tissue is not strong enough to support its own cellular strength. This thought can be illustrated by the following visual experiment:
Take a plastic pop bottle and cut the top and bottom sections off so that you are left with the uniform circular section that typically lies underneath the label. Make a perpendicular cut so that the plastic circle can be opened into a rectangle. Open it and let it go. The plastic 'rolls' in onto itself causing a reduction in diameter. But if a circle of solid material the same diameter as the plastic circle were placed within the pre-cut bottle, the structure wouldn't roll!
Therefore, the presence of such growth is benefical in terms of a tree's mechanical strength. But I would consider such development detrimental when considering the fact that the callus tissue will never be able to form a continuous barrier/seal over the cavity. The edges will not grow together as one, like that of mammalian skin. One must keep in mind that callus tissue forms in response to an inflicted stress upon a tree, such as a limb being ripped off or poor pruning cut. Either way the tree is doing all that it can to sustain life for the time being, even though fungus and other decay organisms can still access the wound and work at the tree's further demise.
Arborists used to recommend and impliment the cleaning, bracing, sealing, and filling/covering of cavities to accelorate compartimentalization and decrease the effects of decay. However, there is no scientific or experimental evidence to support cavity treatment.
The filling of a cavity with concrete was once a common remedy just as wound painting.............but time has taught us, the collective group of arborist, otherwise.
