Pericarp structure and phylogeny within Lamiaceae subfamily Nepetoideae tribe Ocimeae

Abstract

The pericarp structure has been investigated in about 205 species, representing 43 out of the about 50 genera of Lamiaceae subfamily Nepetoideae tribe Ocimeae (Ocimoideae). In its basic structure, the pericarp of Ocimeae corresponds to that of other Nepetoideae. The exocarp has usually both mucilaginous and non‐mucilaginous cells. Below it, there are soft cells (mesocarp), a layer of vertically arranged bone cells and a thin innermost cell layer. The differences discovered in pericarp anatomy essentially agree with the traditional subdivisions of Ocimeae (by e.g. Briquet). The subtribes Hyptidinae and Ociminae and the genus Aeollanthus (in subtribe Plectran‐thinae) have, with few exceptions crystals in the bone cells. Unlike other Labiatae, Plectranthinae (except Alvesia, Isodon and Siphocranion ) has a plate‐like content in the mucilaginous cell. The systematic position of the latter three genera is discussed. Because of their pericarp anatomy, Hoslundia, Fuerstia, Catoferia, Nosema, Benguellia, Octomeron and Ceratanthus are suggested to belong to Ociminae, and Neohyptis to Plectranthinae. On the basis of pericarp characters an informal division of Ociminae is suggested. Considering the distribution of stamen and pericarp characters, the genera Capitanya, Pycnostachys and Solenostemon are suggested to originate from Plectranthus. Ocimeae species which grow in arid habitats tend to produce more mucilage and to have a larger plate‐like content in the mucilaginous cells than species from moist or wet habitats.