Stem: absent or only present as a small cone of tissue.
Spore-mass: whitish, cream-coloured and finally olive-brown.
Spores: small, brownish, minutely warted and spherical, 4-5 µm in diameter and intermixed with thick-walled, branched, brown hyphae, 3-5 µm broad.
Habitat & Distribution: On the ground in copses, at the edges of woods, under hedges or on refuse tips, and sometimes in gardens. It may appear in the same place year after year, and has been recorded growing beneath the rafters in houses.
General Information: When young it is white inside or cream-coloured before the spores have developed and can then be cut into slices and cooked. I have seen it on sale in markets in N. America and it is collected for food by many in Europe. Its pumpkin-shape with a circumference of anything up to 1,050 mm makes this fungus easily recognisable. The number of spores produced by a fruit-body measuring 400 × 280 mm has been calculated by A. H. R. Buller as 7,000,000,000,000 spores!
Calvatia utriformis (Fries) Jaap (= C. caelata (Persoon) Morgan)
has a goblet-like shape and a distinct, sterile base composed of large cells with a prominent membrane separating them from the spore-mass; the spores are 4-5 µm diameter, smooth and spherical.
C. excipuliformis (Fries) Perdeck (= C. saccata (Vahl.) Morgan)
is pestle-shaped with a well developed stem. The spore-mass is composed of warted, globose spores, 4-5 µm in diameter.