Didymium laxifilum G. Lister & J. Ross, 1943

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 laxifilum G. Lister & J. Ross , in G. Lister (1945: 264)

= Didymium aurantipes T.E. Brooks & Kowalski (1966: 169)

Lectotype (designated by Moreno et al. 1997):— UNITED KINGDOM. England: Loughton , Epping Forest , 51.55ºN 0.02ºE, on dead leaves, 19 Jan 1944, G. Lister & H.J. Howard, B.M. 3501[= K(M)38221 ] (K!). Syntype:— UNITED KINGDOM. England: Essex, Loughton, Epping Forest , The Warren , 51.66ºN 0.05ºE, 19 Jan 1944, J. Ross, B.M. 3500 [ BM000500877 !] .

This species is characterised by its reddish stalk, and branching capillitium which is anastomosing into a threedimensional net with thick filaments of violaceous brown to dark brown colour becoming hyaline at the ends. Spores are 10–13 µm in diam., dark purple-brown with a pale zone by LM and verrucose. A smooth area on the spores as indicated by Neubert et al. (1995) is not visible in the type material.

The light microscopic characteristics described here are based on earlier observations of the lectotype material deposited in the fungarium at Kew Gardens ( Moreno et al. 1997), and the preparation of an additional slide for light microscopy from the BM specimen was omitted due to the scarcity of the specimen.

Didymium rubeopus G. Moreno, A. Castillo & Illana is a species that shares the foliicolous growth, as well as overall appearance of the sporocarp, and its reddish stalk ( Moreno et al. 1997). It is clearly differentiated by the capillitium formed by thinner filaments (2–4 µm in diam.), which are more or less parallel, little branched and flexuous, with few globose expansions, and by the smaller spores of 9–11 µm diam. Under SEM this last species shows a spore ornamentation formed by tall warts up to 0.5 µm high, sometimes united and homogeneously distributed on the whole sporal surface. Didymium aurantipes T.E. Brooks & Kowalski , was synonymized with D. laxifilum by Kowalski (1973).