define pollengrain .

Pollen is a microspore produced in the pollen sac of angiosperms or the microsporangium of gymnosperms.

It produces the male gametes. Pollen grains have a hard coat that protects the gametes during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the female cone of coniferous. When pollen lands on a compatible pistil or female cone, it germinates and produces a pollen tube that transfers the sperm to the ovule.