The definition states:
The act of growing inward or into.
So "vegetable ingrowth" can mean vegetables or part of a vegetable that grew into a hole? What are the other meaning that "growing inward" can mean, can it also mean inward of a deliminated area?
In the lime stone in the upper portion of the section there was originally an elaborate model of a Lead Mine, now obliterated with white wash; and at the present time the beds and bands of coal are disintegrated and destroyed by the ingrowth of vegetables.
I am not sure what's meant by model of a lead mine, but they probably mean a real lead mine and that the ingrowth of vegetables grew into the cave and disintegrated and destroyed the beds and bands of coal.