Stemonaria irregularis (Rex) 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 : 157

Stemonaria irregularis (Rex) Nann. -Bremek., R. Sharma & Y. Yamam., in Nannenga-Bremekamp, Yamamoto &

Sharma, Proc. Kon. Ned. Akad. Wetensch., C. 87(4):456 (1984). [Proposed earlier by Nannenga-Bremekamp, Proc.

Kon. Ned. Akad. Wetensch., C 87(4): 505 (1983) but nom. inval., Melbourne Code art. 35.1 (ICBN, art. 43.1)]

≡ Comatricha irregularis Rex, Proc. Acad. Nat. Sci. Philad. 43(2): 393 (1891)

Specimen examined: UNITED STATES OF AMERICA, Ohio, Prof. W.P. Kellerman, Rex 117 [BM001247207 = box, BM001247187 = slide, BM001247195 = SEM stub] (BM).

This species was described by Rex (1891) as Comatricha irregularis based on material from several states in the USA. The type material comes from Fairmont Park, Philadelphia, Pennsylvania ( USA), without indication of the substrate in the protologue, although it is mentioned as occurring on dead wood of trees angiosperm by Martin & Alexopoulos (1969). Stemonaria irregularis has been described in more detail but only with material from Sweden, with photos of its macro- and microscopic characteristics, including photos of spore ornamentation by SEM ( Eliasson et al. 2010). The material studied by us cannot be type material because it has been collected from Ohio, but out observations add for the first time SEM-data for a specimen from North America and confirm that the spore characters of European and North American specimens collected under this name are identical. The genus Stemonaria was established for species with intertwined fibres in the stalk and capillitia without surface net. It is comprised of species removed from the genus Comatricha and Stemonitis . In our opinion, as long as no molecular data are provided to circumscribe the genus Stemonaria and it remains based on morphological characters only, it is a weakly defined genus. Only in order to avoid further taxonomic instability it is accepted here.