Didymium panniforme J. Matsumoto

Moreno, G., Castillo, A. & Thüs, H., 2024, Critical revision of Physarales and Reticulariales (Myxomycetes) at the Natural History Museum London (BM), Phytotaxa 644 (2), pp. 79-101 : 96

Didymium panniforme J. Matsumoto , in Matsumoto & Deguchi (1999: 61)

= Didymium leoninum var. effusum G. Lister (1933: 71)

Lectotype (designated by Lado & Wrigley de Basanta 2018: 30):— JAPAN. Tochigi Prefecture: Nasu, 37º01’11”N 140º07’15”E, 15 Aug 1932, the Emperor of Japan [Emperor Shôwa, Hirohito], box B.M. 4171 [ BM001247522 !], + two corresponding historic slides s.n. [ BM001095145 !, BM001095146 !], + one freshly prepared slide, s.n. [ BM001247533 !] .

This species is characterised by large, broad, flattened plasmodiocarps, richly developed capillitium consisting of a dense network of branched, smooth, thin, pale purplish filaments. Peridium with large, stellate, pointed crystals. Spores pale purplish, globose to subglobose, with ridges already clearly visible by LM but much more marked by SEM.

Lister (1933) regarded this taxon as a variety of Didymium leoninum Berk. & Broome , which has stipitate sporocarps ( Lister 1925, Emoto 1977). The latter author also illustrates plasmodiocarpic forms of this species in his plate 122. Matsumoto & Deguchi (1999) consider it an autonomous species based on its complex sporal ornamentation formed of coalescing crests instead of the fine warts of the spores in D. leoninum and described it under the new name Didymium panniforme J. Matsumoto. It differs from Didymium ochroideum G. Lister and D. obducens P. Karst. by the texture of the peridium, the spore size and the form of the capillitium. This species is only known from the type collection.