Reproductive spores in a mushroom are found in the gills (or pores, in the case of some mushrooms like boletes).

Here's a breakdown:

* Gills: These are the thin, blade-like structures found underneath the cap of many mushrooms. They are packed with microscopic spores.

* Pores: Some mushrooms have pores instead of gills. These are tiny holes on the underside of the cap that lead to chambers where spores are produced.

When the spores are mature, they are released from the gills or pores and dispersed by the wind or other means. If they land in a suitable environment, they can germinate and grow into new mushrooms.