Floral micromorphology and anatomical diversity in Microchilus (Orchidaceae: Goodyerinae)

Neotropical Goodyerinae has a problematic taxonomic history based on minor morphological differences in flowers. Recently, the species of the genus Aspidogyne have been transferred to Microchilus because of strong phylogenetic evidence. Our goal was to identify anatomical and micromorphological characteristics of Micro-chilus flowers that could assist in the morphological characterization of the genus. The labellum presented with up to four papillae types and unicellular papilliform trichomes that have a probable tactile and fragrance-secreting function. Secretory structures were structured in two or four strands, prominent or non-prominent in the spur cavity. The secretory tissue contained amyloplasts and a dense cytoplasm with an abundance of or-ganelles, indicating intense metabolic activity. Trichomes were present in most species. Cells with secretory characteristics present on the sepals and petals were likely to be fragrance-secreting structures. The secretory structures inside the spurs differ in number, structure, and position between species and are responsible for the granulocrine secretion that crosses the fissured cuticle.