Physarum pusillum

The fruiting bodies of Physarum pusillum are a stalked sporangia, often gregarious, between 1–2 mm tall. Each sporocarp has subglobose sporotheca, approximately 0.4–0.5 mm in diameter, and a stalk that is membranous, limeless, longitudinally pleated, widened at the base, and standing either straight or with a slight curve at up to 1.3 mm tall. The upper half of the stalk is translucent and orange or reddish-brown, while the lower half is opaque and dark brown. Its peridium is a single layer and encrusted with granular white to grey-white lime, although it is often orange-brown or reddish-brown and limeless at the base. Its capillitium consists of enlarged, irregular lime nodes, filled with lime granules and connected by hyaline, branching threads. It does not have a columella or pseudocolumella. Spores are globose, black in mass and brown by transmitted light, 8.5–12.5 μm in diameter, and minutely warted. These warts are evenly distributed, with distinct groups of denser, larger warts. They are watery white as plasmodia.

Physarum pusillum is found on both herbaceous and woody plant debris, such as dead leaves and twigs, worldwide, including New Zealand, South Africa, Croatia, and South Africa. In general, P. pusillum favours warm temperate to tropical regions.

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