Homalolejeunea cruegeriana Steph. was described based on material from Trinidad (leg. Crüger) and from Petrópolis, Brazil (leg. Rudolph, leg. Ule). The two collections from Petrópolis are present in the Stephani herbarium in Geneva, and also in BM (L. Ellis, pers. comm.), but the material from Trinidad, which was illustrated in the unpublished Icones by Stephani, could not be located and may be considered lost. Since the Rudolph specimen has gynoecia and therefore fits the original descriptions best (the Ule specimen is sterile), it is designated here as the lectotype. The lectotypification was already proposed by the late Patricia Geissler in sched. but was not formally published. The synonymy of Marchesinia cruegeriana (Steph.) Steph. (as ‘M. cruegeri’) under Archilejeunea fuscescens (Hampe) Fulford, however, was published by Gradstein and Hekking (1989) with credit to P. Geissler. Two further specimens of Marchesinia cruegeriana in G identified by Stephani (published in his species hepaticarum under this name), from Suriname (‘herb. Leiden 258’) and Guadeloupe (leg. L’Herminier), also belong Archilejeunea fuscescens.

The epithet of Marchesinia cruegeriana is frequently spelled ‘cruegeri’ (fide A. Hagborg, e-mail of 27 September 2017), which is based on Stephani’s (1912) erroneous citation of the basionym of the species as ‘Homalolejeunea crügeri’. Probably because of this error, the species has been confused with Lejeunea cruegeri Lindenb. and was cited as ‘Marchesinia cruegeri (Lindenb.) Steph.’ under Lejeunea cruegeri by Gradstein and Buskes (1985) and Gradstein (1994). The latter species is considered a synonym of Dibrachiella parviflora (Nees) X.Q.Shi, R.L.Zhu et Gradst.; =Archilejeunea parviflora (Nees) Steph.

Formal treatment