Didymium vaccinum (Durieu & Mont.) Buchet, 1920

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 : 97

Didymium vaccinum (Durieu & Mont.) Buchet , in Buchet (1920: 110)

= Didymium trochus Lister (1898: 164)

Lectotype (designated by Lado & Wrigley de Basanta 2018):— UNITED KINGDOM. England: Cambridgeshire, Barton , 52.182ºN 0.0562ºE, 8 and 27 Jul 1897, J. Saunders & E. Saunders, B.M. 1904 A [ BM001089123 ] + two historic slides “1”, “3” [ BM001223744 , BM001223745 ]. Studied Syntype:— UNITED KINGDOM. England: Bedforshire , Kitchen End , 52 03’N 0 34’W, 100m, on a “heap of turnips and haulm”, 28 Oct 1897, C. Crouch, B.M. 1708 [ BM000500869 ! ].

Didymium trochus is considered to be a synonym of D. vaccinum ( Lister 1925) . The specimen B.M. 1708 was revised by J. Matsumoto in 1998 and he confirmed it to belong to D. trochus . This species is characterised by whitish to pale ochraceous fructifications, forming globose to hemispherical sporocarps, sessile or with a short stalk; with a thick, crusty double peridium, the outer layer smooth, resembling an eggshell, and the inner layer membranous; with a well-developed whitish hemispherical columella and a rigid filamentous capillitium and characteristically ornamented spores. We have not observed the less developed sporal ornamentation on one side as indicated by Lister (1925) on the studied syntype, but the lectotype specimen still needs to be re-examined for this trait.