‘Saccus’ term is used for

The correct answer is Wings of pollen grains of Pinus.

Explanation:
In the genus Pinus (which belongs to the gymnosperms), pollination occurs primarily through the wind (anemophily).
To adapt to this mode of transport, the pollen grains develop specialized structures that help them float in the air.

During the development of the pollen grain, its outer wall layer—called the exine—extends and inflates outward on two sides to form hollow, air-filled, wing-like structures.
Botanically, each of these air sacs or wings is called a saccus (plural: sacci).
These sacci act like balloons, lowering the overall density and increasing the buoyancy of the pollen grains so they can easily be carried by wind currents to reach the female cones.