Complementary cells are formed by the activity of ..........

Complete the following analogy-type questions:
$(i)$ Wood formed during spring season : Early wood :: Wood formed during winter season : .........
$(ii)$ Bark formed early in the season : Early bark :: Bark formed at the end of the season : ..........

Give differences: Heartwood and Sapwood.

What are $P, Q$ and $R$ in the given anatomical structure?

Lenticels are involved in

Late wood is distinguished from early wood by the presence of: