When the conjoined cambium resumes the development of a continuous layer of xylem and phloem, no further trace of the injury is observable, unless a speck of dead cells remains buried beneath the new wood, and indicates the line where the knife point killed the former cambium and scored the surface of the wood in making the wound.
"Disease in Plants"
H. Marshall Ward
And, well, she has rather a lot of xylem zones-rings, you know.
"The Venus Trap"
Evelyn E. Smith