A number of potentially poisonous, white mushrooms are similar in appearance when they are in their immature button stage and lack a visible stem. Button stage mushrooms differ in that they are smaller (under 4 cm broad) and exhibit the faint outline of gills or other structures when cut in half, rather than having undifferentiated flesh. The poisonous earth balls
(species of Scleroderma
) are superficially similar, but are tan, yellowish or brown rather than white and have a black interior (though when very young, the interior is whitish). A number of other white puffballs differ in being much smaller. Such puffball are generally edible if the exterior is smooth and if the interior is all-white. The edible Lycoperdon excipuliforme
is white when young and can be up to 15 cm broad; it differs in that it is pestle-shaped.