When the primordium gets large enough, the stem elongates and pushes the cap up above the ground. As the stem elongates, the cap expands, a little like an umbrella unfolding. In some mushrooms, the expanding cap breaks a veil-like membrane extending from the cap to the stem, leaving a ring. Some growing mushrooms may also break a second membrane that covers it completely, and dried bits of this broken veil form scales on the cap. On the underside of the cap, the spore-producing basidia are found in several different structures.
Basidia produce four spores at the end of microscopic spines called sterigma.
When the spores are ready, they are discharged a short distance into the space between the gills or teeth, or into the center of the tube. The spores then fall out of the cap and are carried away in the wind. If the spore lands in a good spot, it germinates, producing the mycelium of a new fungus individual. The puffballs are relatives of mushrooms whose basidia and spores are enclosed in a sac instead of covering gills, or in tubes. Coral fungi are also mushroom relatives.