Mushrooms don't have gills in the same way that fish do. The "gills" you're referring to are actually lamellae, which are thin, vertical plates found on the underside of the mushroom cap. These lamellae are crucial for the mushroom's reproduction. Here's what they contain:

* Spores: These are the microscopic reproductive cells of the mushroom. They are produced in large quantities on the surface of the lamellae and are released into the air to spread and create new mushrooms.

* Hyphae: These are the thread-like filaments that make up the mushroom's body. They grow and branch out, forming a network called a mycelium. The hyphae in the lamellae help to support the structure and transport nutrients.

* Pigments: The lamellae often have distinctive colors due to the presence of pigments. These pigments can help to attract insects or other animals that might help to spread the spores.

In short, the lamellae of a mushroom are not gills in the biological sense but are the structures that allow the mushroom to reproduce.