Give short answers:
$(i)$ What is the function of cambium?
$(ii)$ What is meant by lignin? Where is it present?
$(iii)$ What are the characteristics of cells of epidermis?

(N/A) $(i)$ Cambium is the region responsible for secondary growth,which leads to an increase in the thickness or girth of the plant stem and root.
$(ii)$ Lignin is a complex organic polymer that acts as a cementing material,providing structural support and hardening the cell wall. It is primarily present in the cell walls of sclerenchyma tissue,making them lignified and dead at maturity.
$(iii)$ The cells of the epidermis are typically elongated,flattened,and arranged in a single layer without any intercellular spaces. They are living cells that often secrete a waxy,water-resistant layer on their outer surface to protect the plant.