PDD 15937, 24843.

Fruiting body a plasmodiocarp, usually forming gregarious clumps or rosette like masses and sometimes aggregated into a pseudoaethalium or (less commonly) sporangium like and attached to the substrate by a weak, yellow or red, stalk like strand of the hypothallus, the individual plasmodiocarps higher than broad, 0.2–4.0 mm wide and up to 1 mm or more high, the clumps usually 2–3 mm in diameter, frequently much larger. Hypothallus membranous, more or less venulose, colourless to yellowish or reddish brown, sometimes scanty. Peridium consisting of a single layer, membranous, white or grey to brownish or reddish drab with scattered, white or reddish lime deposits. Capillitium dense, elastic, consisting of numerous large, spike like, transverse, white nodes and smaller fusiform nodes connected by delicate, hyaline threads. Spores dark brown in mass, pale violaceous brown by transmitted light, minutely spiny, 7–10 µm in diameter. Plasmodium white, changing to yellow upon exposure to light.

Widespread in the tropics and also reported from several localities in North America (Martin & Alexopoulos 1969, Ing 1999). Reported from New Zealand by Mitchell (1992), based on specimens from Northland and Gisborne.

Soil, surface debris, and often encrusting leaves of living plants.

The fruiting bodies of Physarum gyrosum are quite unlike those of most other members of the genus Physarum, and some authors (e.g., Ing 1999) have considered the species more appropriately placed in the genus Fuligo (as F. gyrosa).