Lejeunea (sect. Xenantholejeunea) G. E. Lee & Gradst., comb. et stat. nov.

[Clade XIV]Lejeunea sect. Xenantholejeunea(R. M. Schust.) G. E. Lee & Gradst. comb. et stat. nov. Taxilejeunea subg. Xenantholejeunea R. M. Schust. (Schuster 1980: 1166) Type species Lejeunea umbilicata (Nees) Nees. Description Plants relatively large, 1.0–2.0 mm wide. Stem epidermis cells large, ca 3–6 times larger than medullary cells, sometimes strongly bulging outwards, medullary cells in 10–50 rows. Leaf cells with distinct trigones and frequent intermediate thickenings, up to 4 per cell. Lobules frequently with a large disc cell. Male bracteoles restricted to the base of the male spike. Innovations usually repeatedly fertile. Perianths 0–5 - keeled, with or without a beak. Asexual reproduction by specialized devices absent (regeneration from leaf margins observed in L. umbilicata). Distribution Indo-Pacific. Species Lejeunea albescens (Steph.) Mizut., L. asperula (Steph.) Mizut., L. fleischeri (Steph.) Mizut., L. kinabalensis Mizut., L. lumbricoides (Nees) Nees, L. microloba Taylor, L. mizutanii Grolle, L. pectinella Mizut., L. umbilicata, L. utriculata (Steph.) Mizut., L. vitiensis G. E. Lee & Pócs. Notes Lejeunea sect. Xenantholejeunea, a former infrageneric group of Taxilejeunea, is characterized by relatively robust, dioicous plants with stems with highly enlarged epidermis cells and numerous medullary cells (up to 50 in rows), distinct trigones and intermediate cell thickenings, usually repeatedly fertile innovations, and absence of asexual reproduction by specialized devices. The section contains a robust, morphologically distinct subclade (BS 100, PP 1.00) consisting of L. lumbricoides, L. mizutanii, L. pectinella, L. utriculata, L. fleischeri, and L. vitiensis. Characteristic of this subclade are the recurved leaf apex, both in moist and dry conditions, the relatively large lobules, and the presence of a large, rectangular disc cell on the apical margin beyond the first tooth. The group is not formally described as it would render sect. Xenantholejeunea paraphyletic. A further subclade consisting of L. albescens, L. asperula, L. microloba, and the type of the section, L. umbilicata, stands out by having a terete, eplicate perianth without a beak. This subclade is not well-supported, however, and is therefore not described. References Eifrig (1937), Lee (2013).