The systematic position of the moss genus Rhacocarpus

摘要

Rhacocarpus Lindb, has traditionally been placed in the Hedwigiaceae, but recent workers have removed it from the family and either left it unassigned to a family to placed it in an untenable one. The genus is studied and a detailed description of itis presented. Based on the position of perichaetia, on ecostate leaves with thick-walled porose cells and well developed alar cells, and on tetrahedral spores, it is postulated that Rhacocarpus should be placed in its own family, the Rhacocarpaceae, in the Dicranales, in the vicinity of the Dicnemonaceae. Wardia Harv. & Hook. is briefly discussed. Its morphology suggests that it too is an acrocarpous moss and although no formal placement is offered, the Seligeriaceae are suggested as a potentially fruitful lineage to investigate.