Are Plagiothecium cavifolium, P. nemorale and P. succulentum indeed variable species ?

摘要

This article compiles all available morphological and anatomical data on the gametophyte of three species of Plagiothecium genus which are considered to be the most taxonomically difficult. It presents a range of variation of all the described characteristics of these species and summarises the characteristics considered by individual researchers as taxonomically important. The article shows that among all the features qualitative characteristics related to stem leaves of the described species dominate. Results suggest not only a wide range of variability of the described features or the overlapping of their ranges, but also a lack of clear criteria which could be used to distinguish Plagiothecium cavifolium , P . succulentum and P . nemorale from one another.