Puffballs are fungi, so named because clouds of brown dust-like spores are emitted when the mature fruitbody bursts or is impacted. Puffballs are in the division Basidiomycota and encompass several genera, including Calvatia, Calbovista and Lycoperdon. True puffballs do not have a visible stalk or stem. The puffballs were previously treated as a taxonomic group called the Gasteromycetes or Gasteromycetidae, but they are now known to be a polyphyletic assemblage. The distinguishing feature of all puffballs is that they do not have an open cap with spore-bearing gills. Instead, spores are produced internally, in a spheroidal fruitbody called a gasterothecium. As the spores mature, they form a mass called a gleba in the centre of the fruitbody that is often of a distinctive color and texture. The basidiocarp remains closed until after the spores have been released from the basidia. Eventually, it develops an aperture, or dries, becomes brittle, and splits, and the spores escape. The spores of puffballs are statismospores rather than ballistospores, meaning they are not forcibly extruded from the basidium. Puffballs and similar forms are thought to have evolved convergently from Hymenomycetes by gasteromycetation, through secotioid stages. Thus, 'Gasteromycetes' and 'Gasteromycetidae' are now considered to be descriptive, morphological terms but not valid cladistic terms. Stalked puffballs do have a stalk that supports the gleba. None of the stalked puffballs are edible as they are tough and woody mushrooms. The Hymenogastrales and Enteridium lycoperdon, a slime mold, are the false puffballs. A gleba which is powdery on maturity is a feature of true puffballs, stalked puffballs and earthstars. False puffballs are hard like rock or brittle. All false puffballs are inedible, as they are tough and bitter to taste. The genus Scleroderma, which has a young purple gleba, should also be avoided. Puffballs were traditionally used in Tibet for making ink by burning them, grinding the ash, then putting them in water and adding glue liquid and "a nye shing ma decoction", which, when pressed for a long time, made a black dark substance that was used as ink.
While most puffballs are not poisonous, some often look similar to young agarics, and especially the deadly Amanitas, such as the death cap or destroying angel mushrooms. It is for this reason that all puffballs gathered in mushroom hunting are cut in half lengthwise. Young puffballs in the edible stage, before maturation of the gleba, have undifferentiated white flesh within; whereas the gills of immature Amanita mushrooms can be seen if they are closely examined. The giant puffball, Calvatia gigantea, reaches a foot or more in diameter, and is difficult to mistake for any other fungus. It has been estimated that a large specimen of this fungus when mature will produce around 7 × 10¹² spores. If collected before spores have formed, while the flesh is still white, it may be cooked as slices fried in butter, with a strong earthy, mushroom flavor. Not all true puffball mushrooms are without stalks. Some may also be stalked like the Podaxis pistillaris which is also called the "false shaggy mane". There are also a number of false puffballs that look similar to the true ones.
