BPI 807539.

Fruiting body a stalked or sessile sporangium (or occasionally plasmodiocarpous), closely gregarious and sometimes compacted in small groups within the larger fruiting, 1.0–1.5 mm tall. Sporotheca globose to turbinate or reniform, 0.3–1.0 mm in diameter. Stalk, when present, irregular, usually tapering upward, deeply plicate-furrowed, opaque, dark or covered with white calcareous granules. Hypothallus membranous, more or less contiguous for a group of fruiting bodies, colourless to brown. Peridium consisting of a single layer, membranous, usually densely incrusted with ashy white calcareous deposits, especially above, and then white or greyish white, but sometimes nearly limeless and then more or less iridescent. Columella absent. Capillitium abundant, consisting of a network of rather long hyaline threads connecting white lime nodes that vary considerably in size and shape, occasionally somewhat massed towards the centre of the sporotheca. Spores very dark brown to black in mass, olivaceous brown by transmitted light, minutely warted, mostly 10.0–11.5 µm in diameter. Plasmodium white or grey.

Known from Asia (Yamamoto 1998), Europe (Ing 1999), North America (Martin & Alexopoulos 1969), and South America (Farr 1976). Reported (as Physarum connatum) from New Zealand by Rawson (1937), based on specimens collected in South Canterbury and Southland.

Decaying wood and bark.

As pointed out by several authors (e.g., Hagelstein 1944, Martin & Alexopoulos 1969), this is a very variable species. Typical fruitings of mostly stalked sporangia usually can be recognised on the basis of the small groups of compacted sporangia, but when these are not evident or the stalk itself is poorly developed, Physarum notable is often very difficult to identify. In the latter instance, the sporangia can resemble those of several other species, including P. leucophaeum or P. compressum (Farr 1976).