(a) rosette tier

Explanation:

In Pinus, the third tier of embryonal cells from below is known as rosette tier. The four lower most cells which are far from the micropolar end are called the embryonal tier. These develop into an embryo. The cells above the embryonal tier called the suspensor tier and the third tier from below is called the rosette tier. The free nuclei tier are formed of 4 nuclei. It is the fourth upper most tier.