Paradiacheopsis rigida (Brândză) Nann.

Moreno, G., Castillo, A. & Thüs, H., 2018, Critical revision of type material of Stemonitales (Myxogastria) at the Natural History Museum London (BM), Phytotaxa 344 (2), pp. 149-159 : 156

Paradiacheopsis rigida (Brândză) Nann. -Bremek., in Martin & Alexopoulos, Myxomycetes : 231 (1969)

≡ Comatricha laxa var. rigida Brândză, Ann. Sci. Univ. Jassey 11: 126 (1921)

≡ Paradiacheopsis rigida (Brândză) Nann. -Bremek., Proc. K. Ned. Akad. Wet., Ser. C, Biol. Med. Sci. 70: 209 (1967) nom. inval., Melbourne Code art. 41.5 (ICBN, art. 33.3), basionym reference omitted.

Lectotype (hic designatus):— MOLDAVIA, July 1919, on dead wood, Dr. M. Brândză BM 4021 [ BM001088434 = box, BM001247188 = slide, BM001247196 = SEM stub].

This species has been misinterpreted by different authors as already indicated by ING (1999). The description and illustrations of this author are similar to Brândză’ s material, preserved in BM and studied by us. Moreover, in our opinion the illustrations by Poulain & al. (2011) do not correspond to this species, because the figures for the specimens have a longer stalk, and the capillitium shows branches thinner than the specimen studied by us. Martin & Alexopoulos (1969) indicate in the observations of Comatricha laxa that C. laxa var. rigida has not been studied. He referred instead to data by Hagelstein (1944) based on material from Minnesota. The Minnesota material is described with scant capillitium and very rigid threads. This description is similar to that given by Lister (1925), who also measured spores with a diameter of 8–13 μm and with spinulose ornamentation. Nannenga-Bremekamp (1991) compares C. laxa var. rigida (under its synonym Paradichaeopsis rigida ) with Paradiacheopsis solitaria (Nann.-Bremek.) Nann.- Bremek. She indicates that the size of the spores is different: P. solitaria produces spores of (12–) 14–16 (–20) μm in diameter, while for P. rigida 7–9 (–11) μm were measured. However she notes that the illustrations of P. rigida could represent a modification of P. solitaria with particularly small spores. The other features are very similar (sporocarp size, development of capillitium, and size of the stalk). It is unknown, how many duplicate sets of Brandza’s collection have been dispersed as syntypes and in which collections they are housed today. We therefore cannot be sure that it is all homogenous. The specimen studied by us represents a well developed example of this species and the label information fits the protologue, we therefore chose it as the lectotype in order to fix the long disputed interpretation of this name.