Gymnanthemum amygdalinum (Delile) Sch. Bip. ex Walp. belongs to the Asteraceae family and is commonly called as alumã or macela-grande by the Brazilian population. It is a shrub whose leaves are employed for hepatic and gastric disorders in folk medicine. Sesquiterpenoid lactones, triterpenoids and flavonoids are often the phytochemicals isolated from the species. Different pharmacological essays have demonstrated analgesic, anti-inflammatory and antimicrobial activities. As it lacks morphological information on G. amygdalinum, this investigation has carried out anatomical studies of the vegetative aerial organs in order to contribute to its morpho-diagnosis.

Specimen samples from the spontaneous flora were collected in Palotina, city situated in the West of Paraná, in 2005. The herbarium voucher was registered at the Museu Botânico Municipal de Curitiba – PR. Adult leaves and fragments of the stem were fixed in FAA70 and kept in 70% EtOH. The material was sectioned by free-hand and stained either with toluidine blue or astra blue-basic fuchsine.

The leaf epidermis is uniseriate and coated with a thin and striate cuticle. In surface view, the epidermal cells show wavy contour. Anomocytic stomata are encountered on both surfaces, being more frequent on the abaxial side, and are inserted on the same level as the adjacent cells. Non-glandular trichomes, pluricellular and uniseriate occur. Glandular trichomes are capitate, pluricellular and biseriate, located in small epidermal depressions. The mesophyll is dorsiventral, composed of one row of palisade parenchyma and several layers of spongy parenchyma. The midrib are biconvex and the petiole plain-convex, both traversed by numerous collateral vascular bundles, arranged in open arc. In the stem, the uniseriate epidermis shows glandular and non-glandular trichomes similar to the leaf. Below the dermal system, it occurs tangential collenchyma, several layers of cortical parenchyma bearing chloroplasts, and an endodermis with Casparian strips. The vascular cambia form phloem outwards and xylem inwards. Sclerenchymatic caps are found next to the phloem and the pith has large parenchymatic cells.