PDD 69453.

Fruiting body a sessile or stalked sporangium, densely crowded or aggregated, sometimes to the point of forming a pseudoaethalium. Sporotheca cylindrical or ovoid, 0.5–1.3 mm tall and 0.4–0.6 mm in diameter. Stalk, when present, weak, membranous, often flattened, white, representing an extension of the hypothallus. Hypothallus prominent, contiguous for a group of sporangia, membranous, strongly calcareous, white. Peridium consisting of two layers, the outer layer crustose, calcareous, white, fragile, readily falling away but with the apical portion sometimes remaining as a cap, the inner layer membranous, grey (sometimes with purple tints), dehiscence more or less irregular. Columella absent, but a pseudocolumella sometimes present. Capillitium dense, consisting of angular or rounded, white lime nodes connected by short, hyaline threads. Spores black in mass, very dark purplish brown by transmitted light, often angular or irregular in shape, minutely and very densely spiny, sometimes paler and smoother on one side, 12–15 µm in diameter. Plasmodium white or watery grey.

Considered as cosmopolitan by Martin & Alexopoulos (1969) but apparently rare at high latitudes (Stephenson et al. 2000). Not reported in print as occurring in New Zealand but represented by a specimen from Auckland.

Decaying wood, bark, and other types of plant debris.

Martin & Alexopoulos (1969), Nannenga-Bremekamp (1991), Neubert et al. (1995), Ing (1999).

Physarum didermoides produces extensive fruitings that are not easily overlooked. The presence of only a single collection in PDD at least suggests that the species is uncommon in New Zealand. Interestingly, P. didermoides is one of the more common members of an ecological group of myxomycetes associated with decaying inflorescences of large tropical herbs (Schnittler & Stephenson 2002).