Three new synonyms of <i>Macromitrium microstomum</i> (Hook. &amp; Grev.) Schwägr. (Bryophyta, Orthotrichaceae), with comments on its morphological variations

<i>Macromitrium filicaule</i> Müll.Hal., <i>M. pacificum</i> var. <i>brevisetum</i> Thér. and <i>M. subnitidum</i> Müll.Hal are placed in synonymy with <i>Macromitrium microstomum</i> (Hook. &amp; Grev.) Schwägr. The morphological variations of <i>M. microstomum</i> branch leaves, perichaetial leaves and capsules are illustrated by digital images.