ABSTRACT
Abstract The present study is aimed for anatomical characterization of nine taxa of Acmella to supplement data specifically for its current sectional classification and species circumscriptions. Anatomical characterization of this genus is little explored. This study focuses on internal structure of leaves, petioles, peduncles, stems, roots and cell inclusions to determine its taxonomic importance. In stem anatomy the number of hypodermal collenchymatous layers and the arrangement of parenchymatous cortex together place an important role in the identification of Acmella. Root anatomy was similar in all the examined taxa except in the arrangement of xylem vessels. In A. tetralobata xylem vessels arranged in pentarch fashion while rest of the species possess tetrarch arrangement. Several cellular inclusions such as calcium oxalate crystals and oil bodies were observed. The petioles were crescent shaped having bifacial surfaces with both surfaces pubescent. Peduncles possess ridges and furrows in its outline. The leaves are dorsi ventral and possess single layered epidermal cells covered with cuticle having anomocytic, anisocytic and diacytic types of stomata in both adaxial and abaxial surfaces. The present study provides a tool for the microscopic identification of the genus.