Calvatia cyathiformis

Initially the fruit body is globular but when mature is roughly pear-shaped, usually with a markedly narrower, sterile base and masses of powdery spores held within a mass of ‘cotton-wool’ in the upper area. The fruit body may grow to more than 15 centimetres across. Initially it is solid, white throughout, with a smooth skin. Later the skin becomes becomes brown then purplish. The upper flesh changes to powdery+‘cotton-wool’ and becomes purplish-brown or greyish-purple. The skin, a millimetre or so thick, cracks polygonally and falls away in fragments, so exposing the spores to wind dispersal.

The sterile base is well-developed and internally spongy (with cavities up to 1 mm wide) and may remain long after all spores have gone. There is a membrane between it and the spore-bearing area.

 The fruit bodies appear on the ground, often in open, grassy areas.

Look-alikes

Spores of most puffballs and the like are a (definitely non-purplish!) shade of brown. Scleroderma may have purplish spores but the skin is very thick and does not break and fall away. Rather, several cracks form at the top of the fruit body and segments of skin fold outward to expose the spore mass (in which there is no ‘cotton-wool’).

Australian purplish-spored Calvatias have often been identified as Calvatia lilacina, which may be just  a synonym of Calvatia cyathiformis. If kept as a separate species, Calvatia lilacina fruit bodies are  smaller (possibly up to 10 centimetres) and without a well-developed base. If present the base is rudimentary and composed of small, compacted cells. Calvatia cyathiformis was first reported in 1811 (based on North American material) and Calvatia lilacina in 1845 (based on Western Australian material). The 1811 report included two drawings of just the bases (see https://canberra.naturemapr.org/Community/Sightings/Details/4198286).