Final answer:
In spring, with lots of water and wide xylem cells in the walls, Cambium forms. Cambium is responsible for the seasonal growth rings seen in trees as it produces secondary xylem, known as spring wood.
Step-by-step explanation:
What forms in the spring when there is lots of water and xylem cells are wide within cell walls? The correct answer is Cambium.During the spring growing season, the activity of the vascular cambium results in the production of cells of the secondary xylem, which have a large internal diameter and their primary cell walls are not extensively thickened. This is known as early wood, or spring wood. As the vascular cambium continues to be active, it produces secondary xylem cells that contribute to the visible annual growth rings in a tree's stem. Cambium is a layer of tissue located between the wood and the inner bark that is responsible for the secondary growth of stems and roots. Therefore, in spring, with abundant water availability and the characteristic of having wide xylem cells, it is the vascular cambium that is forming.