Lejeunea (sect. Glaucescentes) R. M. Schust.

[Clade II]Lejeunea sect. GlaucescentesR. M. Schust. (Schuster 1980: 1001) Lejeunea subg. Taxilejeunea Spruce (Spruce 1884: 212) – Type species: L. pterigonia (Lehm. & Lindenb.) Mont. (lectotype, designated by Jones 1967). Sphaerolejeunea Herzog (Herzog 1938: 88) – Type species: S. umbilicata Herzog. ? Lejeunea subg. Neopotamolejeunea (M. E. Reiner) Gradst. & M. E. Reiner (Gradstein and Reiner-Drehwald 2007: 487) – Type species: L. juruana Gradst. & M. E. Reiner. Type species Lejeunea glaucescens Gottsche. Description Plants mostly autoicous (occasionally dioicous). Stem epidermis as in sect. Macrolejeunea. Oil bodies granular (homogeneous in L. aquatica and L. topoensis). Gynoecial innovations present and usually repeatedly fertile, with 2–10 gynoecia in a row. Perianths eplicate or shortly plicate, keels smooth or toothed. Asexual reproduction by specialized devices absent. Distribution Pantropical. Species Lejeunea aquatica Horik., L. conformis Nees & Mont., L. debilis (Lehm. & Lindenb.) Nees & Mont., L. drehwaldii Heinrichs & Schäf. - Verw., L. eifrigii Mizut., L. flaccida Lindenb. & Gottsche (= L. obtusangula Spruce), L. furcicornuta (Grolle) G. E. Lee & Pócs, L. glaucescens Gottsche, L. pterigonia (Lehm. & Lindenb.) Mont., L. serpillifolioides (Raddi) Gradst. (= L. isocalycina (Nees) Prantl), L. sulphurea (Lehm. & Lindenb.) Spruce, L. terricola Spruce, L. topoensis Gradst. & M. E. Reiner, Lejeunea sp. 1. (= “ L. sikorae (Steph.) Steph. ”, Figs 5, 6). Notes This section contains many former members of the genus Taxilejeunea, a group of species with elaborate stems made up of highly enlarged epidermis cells and rather numerous medullary cell rows, and with repeatedly fertile innovations resulting in gynoecia and perianths arranged in rows of 2–10 gynoecia. Underleaves vary considerably in size, and some species have very large and strongly auriculate underleaves. The position of L. drehwaldii in sect. Glaucescentes is somewhat unexpected as it differs from other members of this section in having leaves bordered by hyaline cells and sterile or no innovations. The aberrant morphology of the species, which was previously placed in a separate genus, Sphaerolejeunea, is reflected by its position on a long, although unsupported branch. The position of L. aquatica and L. topoensis in the Glaucescentes clade is unexpected as these species have homogeneous oil bodies characteristic of sect. Lejeunea. Moreover, L. aquatica is very similar to L. japonica, a member of sect. Lejeunea, differing from the latter only in smaller lobules, slightly thick-walled stem cells, and the semi-aquatic habitat (Mizutani 1961). The latter characters, seen also in L. topoensis, are usually interpreted as adaptations to the riverine habitat (e. g. Gradstein and Reiner-Drehwald 2007). Further study including the type of the rheophilous subgenus Neopotamolejeunea to which L. topoensis has been assigned, are needed to clarify the taxonomic position of these two riverine Lejeunea species. References Reiner-Drehwald and Drehwald (2002), Gradstein and Reiner-Drehwald (2007), Bastos and Gradstein (2020), Gradstein (2021).