Given a scientific passage and an answer, generate a question for the given answer.

Passage: Pollen is a tiny male gametophyte enclosed in a tough capsule. Pollen carries sperm to an ovule while preventing the sperm from drying out. Pollen grains can't swim, but they are very light, so the wind can carry them. Therefore, they can travel through air instead of water. Answer: pollen
What is the tiny male gametophyte enclosed in a tough capsule?