Final answer:
In layering, a cut is made in the cambium to promote new root growth. The cortex and pith of a stem are made of parenchyma cells. To date a tree using dendrochronology, scientists look at the secondary xylem.
Step-by-step explanation:
When we make a cut in layering, we are trying to selectively cut the cambium. The cambium is a layer of tissue that's actively involved in cell division, and it's located between the xylem and phloem. Through cutting the cambium, it induces the formation of new roots along the stem of the plant during the process of vegetative propagation known as layering.
The cortex and pith of the flax stem are composed of parenchyma cells. Parenchyma cells are a type of simple tissue, characterized by having only one type of cell. They are involved in storage, photosynthesis, and other functions within the plant.
In dendrochronology, or the dating of tree ages through annual rings, scientists examine the secondary xylem. This is because the secondary xylem forms concentric rings each year, which can be counted to determine the age of the tree.