A lectotype for Breutelia chrysocoma (Hedw.) Lindb., (Bryophyta; Bartramiaceae)

A lectotype for Mnium chrysocomum Hedw. (Breutelia chrysocoma (Hedw.) Lindb.) is designated herein. The presence of Schwägrichen's writing on the herbarium sheet for this taxon in G and the confusion of the name with Bartramia arcuata Sw. and Mnium arcuatum Dicks. ex With. necessitated the correct designation of the nomenclatural type. The protologue, single herbarium sheet for M. chrysocomum in the Hedwig-Schäwgrichen collection (G [G00040056]), the cited earlier illustrations of this entity and specimens in the herbaria of Turner (BM) and Dickson (BM) were taken into consideration to determine the most appropriate material for typification. The original sheet for M. chrysocomum in the Hedwig-Schwägrichen collection (G [G00040056]) contains material that possibly originated from the Dickson herbarium (BM) and was probably used by Hedwig for his 1801 description, along with Dickson's own description of the plant, to produce his protologue for M. chrysocomum in Species muscorum frondosorum. However, one of the four entities on sheet G00040056 is of unknown origin, and its inclusion on the sheet may postdate the publication of the species. It is clearly desirable to designate a lectotype specimen for M. chrysocomum from among the remaining plants. Sheet G00040056 is labelled in the hand of Schwägrichen, although in this case the material itself is annotated by Schwägrichen as being that of Hedwig. The issue of herbarium sheets for taxa described by Hedwig, but apparently labelled and annotated by Schwägrichen, is discussed herein