SEM differences in sporophyte micromorphology of Plagiothecium nemorale and P. longisetum (Plagiotheciaceae, Bryophyta)
Plagiothecium nemorale sensu lato is described as a variable Eurasian taxon. Recent studies indicate that this variability is reflected in both qualitative and quantitative features of its gametophyte and its genetic variation. This taxon comprises at least two separate species: P. nemorale (Mitt.) A. Jaeger and P. longisetum Lindb. The present paper examines whether the gametophyte variability of these species is reflected in the micromorphological variation of the sporophyte. The analysis revealed that the seta of P. nemorale is shorter than that of P. longisetum. In addition, regarding the exostome teeth, the lower portion of the outer surface is characterised by loosely-arranged, moniliform cristae in P. nemorale, with conical papillae on the upper side; however, in P. longisetum it possesses tightly arranged, epapillose cristae, with clearly flattened papillae on the upper side. In addition, the inner surface is more gently papillose in P. nemorale than in the latter. These findings not only describe hitherto unknown features of the sporophyte of these species, but also justify the resurrection of P. longisetus as separate from P. nemorale.