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• L. subg. Rheocaulon is monospecific and with leaves have a single vascular bundle • L. subg. Calycocephalus have a greater number of infrageneric taxa • Specialized substomatal chambers characterized the species of L. subg. Eleutherandra • Multilayered cylindric pericycle characterized the species of L. subg. Stephanophyllum • The scapes have always the number of ribs to half the number of vascular bundles Leiothrix is endemic to South America with 47 species, only two of which do not occur in Brazil. Its distinguishing characters are habit, dialypetalous or gamopetalous corolla of the male flowers and presence or not of pseudovivipary. According to Ruhland's monograph (1903) there are five subgenera. Recent molecular and morphological analyses of the family show the genus to be monophyletic, but infrageneric relationships are not well established. The study objective was to investigate leaf and scape anatomy of representatives of the four subgenera that occur in Brazil in order to contribute to the taxonomy and better understand the plants' environmental adaptations. Leiothrix anatomy is similar to that of other Eriocaulaceae genera: leaves and scapes have a single-layered epidermis, collateral vascular bundles are surrounded by a double sheath, leaves have stomata only on the abaxial side, and scapes have alternating vascular bundles of larger and smaller size. Leiothrix subg. Rheocaulon is monospecific, leaves have a single vascular bundle, scapes lack ribs, the epidermal cells have slightly thickened walls, and the cortex contains collenchyma and chlorophyllous parenchyma. In L. subg. Eleutherandra the leaf epidermis cell walls have homogeneous thickening at the margins, specialized substomatal chambers, a hypodermis, and sclerenchymatous extensions of the vascular bundle sheaths. Most taxa of L. subg. Calycocephalus have smaller vascular bundle sheath extensions facing both surfaces and ribbed scapes. Species from Minas Gerais have a hypodermis and up to seven leaf vascular bundles; those from Bahia lack a hypodermis and have more than seven leaf vascular bundles. L. subg. Stephanophyllum has scapes with a cylindric multilayered pericycle with thickened and lignified cell walls. These anatomical structures partly corroborate the subgenera proposed by Ruhland, suggest the existence of other infrageneric groups and reflect the environmental adaptations of the studied species. [ABSTRACT FROM AUTHOR]

Abstract: In Cyperaceae, leaf anatomical characters, in particular the presence of a hypodermis or of a multiple epidermis, have contributed in taxonomic and phylogenetic studies. In this family, the leaf epidermis is often described as uniseriate, and the cells of the subepidermal layers having no chloroplasts are treated as hypodermis. Both tissues have a different ontogenetic origin and hence are not homologous. The aim of the present work was to verify the origin of the subepidermal layers in eight species belonging to Cyperoideae. All species studied presented multiple epidermal layers that were confirmed by leaf ontogeny. In Fimbristylis complanata, F. dichotoma, Pycreus flavescens and P. polystachyos the mature leaves present multiple epidermal layers with cells of the distinct layers similar in shape and size; in the other species studied these cells are different. Especially in the latter case, a multiple epidermis is easily interpreted erroneously as a hypodermis, possibly leading to erroneous evolutionary conclusions. Making correctly distinction between a hypodermis and a multiple epidermis, and hence in case of doubt investigating the origin of the questioned tissue, is compulsory in order to use both characters in a phylogenetic context. Though in the past often called ‘hypodermis’, our leaf ontogenetical observations show that in all species studied, the subepidermical layers constitute a multiple epidermis, originating from the protodermis. [Copyright &y& Elsevier]