Review of the genus Rectolejeunea (Lejeuneaceae, Marchantiophyta)

Based on the examination of types and additional specimens, the 68 taxa originally described under Rectolejeunea are here assigned to five genera - Rectolejeunea, Cheilolejeunea, Cyclolejeunea, Lejeunea and Microlejeunea - or treated as 'doubtful names'. Rectolejeunea is characterized by: ventral merophyte 2 cells wide; leaf cells small and +/- equally thickened, ocelli scattered in leaf lobe and at the leaf base; lobule inflated, apical tooth 1-celled, often long and falcate, hyaline papilla proximal; underleaves bifid, with or without ocelli, lateral margins entire, angulate to dentate; gynoecia with 1 pycnolejeuneoid innovation, perianth compressed, 5-keeled, dorsal keel short and inconspicuous; asexual reproduction by caducous leaves, in normal shoots or in flagelliform branches. The results are presented in three parts: 1. An alphabetical list of taxa described in Rectolejeunea with their accepted names. 2. A discussion of the present concept of the genus Rectolejeunea s.str. and its subgenera, with a key to the five species here accepted (Rectolejeunea berteroana, R. emarginuliflora, R. flagelliformis, R.truncatiloba and R. queenslandica), as well as their types, synonyms, references, geographical distributions, and additional specimens examined. 3. A taxonomic arrangement of the excludenda and doubtful names, with types, synonyms and references. Two new combinations (Cheilolejeunea riparia and Lejeunea bornmuelleri), fifteen new synonyms and seven lectotypifications are proposed. Illustrations of Rectolejeunea berteroana, R. emarginuliflora, R. flagelliformis, Cheilolejeunea assurgens and C. papulosa are provided.