Explanation:
The vascular cambium, a thin layer of cells sandwiched between the wood and bark, produces the secondary vascular tissues: the wood, which is secondary xylem, and the inner bark, which is secondary phloem.

Reference: Biology By Eldra Solomon, Linda Berg, Diana W. Martin, Page no: 720.

Explanation:
Symmetry
Animals can be categorised on the basis of their symmetry.
• When any plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry. Coelenterates, ctenophores and echinoderms have this kind of body plan.
• Animals like annelids, arthropods, etc., where the body can be divided into identical left and right halves in only one plane, exhibit bilateral symmetry.
• Sponges are mostly asymmetrical, i.e., any plane that passes through the centre does not divide them into equal halves.

Reference: NCERT Biology Text, Class: XI, Unit I: Diversity in the Living World, Chapter 4: Animal Kingdom, Page: 47.