The mushroom or puffball fruiting body is produced when the mycelium has become large enough and conditions are right. The mushroom or puffball produces and then releases spores. When these spores germinate, the cycle is repeated. On the underside of the cap are thin plates of tissue, called gills. These produce the spores.
Young puffballs are uniformly white with a firm inside and a thin and fragile outer skin.
As a puffball matures, all or a large portion of the white interior becomes yellow, then darker until it eventually becomes a dry, powdery, dark green to purple to brown spore mass. The thin outer skin may remain intact except for a hole at the top, or it may break away in large, irregular pieces. There are many kinds of puffballs, ranging in size from less than an inch to more than a foot, and weighing several pounds. Most puffballs become noticeable in late summer and fall. Since mushroom and puffball fungi grow on decaying organic matter, they are most likely to form on tree stumps, tree roots, or in other spots in the lawn with high organic debris.