Didymodon validus Limpr. is not universally recognised as a species in its own right but it is often considered a variety, D. rigidulus Hedw. var. validus (Limpr.) Düll. The epithet validus was used at varietal rank only in 1923, as Barbula rigidula (Hedw.) Mitt. var. valida (Limpr.) Broth., but this taxon was actually recognised as a variety, B. rigidula var. gigantea Schlieph. ex Warnst., already in 1904, and this name is lectotypified herein. Accordingly, the transfer of this variety to Didymodon Hedw., as D. rigidulus var. giganteus (Schlieph. ex Warnst.) Ochyra & Bednarek-Ochyra, comb. nov., is effected. This is the correct name for this Central European-Central Asian montane taxon at variety rank. Didymodon validus is considered a new synonym of D. rigidulus var. giganteus.
The taxonomic and nomenclatural history of the broadly conceived genus Bryum Hedw. is briefly outlined. Twenty-one species, originating mostly from the Southern Hemisphere and traditionally classified in this genus, have been transferred to the widely accepted segregates of Bryum, including six in Imbribryum N. Pedersen, three in Leptostomopsis (Broth.) J. R. Spence & H. P. Ramsay, one in Plagiobryoides J. R. Spence, nine in Ptychostomum Hornsch. and two in Rosulabryum J. R. Spence.
The type material of Racomitrium canescens (Hedw.) Brid. fo. erythrophyllum Sakurai from Japan is taxonomically evaluated. This form perfectly falls within the range of variation of Dilutineuron corrugatum (Bednarek-Ochyra) Bednarek- Ochyra, Sawicki, Ochyra, Szczecińska & Plášek and, accordingly, R. canescens fo. erythrophyllum is reduced to synonymy with this species name.
A taxonomic and nomenclatural history of the moss genus Pterogonium Sw. is outlined and the illegitimacy of this name is confirmed. Nogopterium Crosby & W. R. Buck, the name of a new genus erected to replace the illegitimate Pterogonium, is accepted as validly published. This genus consists of five species, two of which, N. coreense (Cardot) Tad. Suzuki and N. tenellum (Tad. Suzuki & Z. Iwats.) Tad. Suzuki, have only recently been transferred to this genus. The transfer of the fifth species, N. tsilingense (P. C. Chen) Tad. Suzuki ex Ochyra & Bedn.-Ochyra, comb. nov., is effected in the present account.