The genus Ormosia (Fabaceae-Faboideae) is common in the neotropics and includes different
species used in folk medicine for various purposes. Ormosia arborea is a tree popularly known as “olho-decabra” and used for its contraceptive effects in Brazilian rural communities. As it lacks data about this
medicinal plant, this work has carried out anatomical studies on the leaf of this potential vegetal drug.
Fully-expanded leaves were fixed and prepared according to light and scanning electron microscopic techniques. Microchemical tests were also carried out. The leaf has paracytic stomata confined to the abaxial
side. The cuticle is smooth and there are bicellular non-glandular trichomes predominantly on the abaxial
surface. The mesophyll is dorsiventral and traversed by minor collateral vascular bundles with sclerenchymatic and crystalliferous bundle sheaths which may attain the epidermis. The midrib is concaveconvex in transection and has one major collateral vascular bundle in circular arrangement and one or
two minor ones, each of which encircled by a sclerenchymatic bundle sheath. The petiole is circular in
transection and possesses a ring of numerous collateral vascular bundles enclosed in a conspicuous sclerenchymatic sheath. Some cells bearing phenolic compounds and prismatic crystals of calcium oxalate are
also present in the leaf.Colegio de Farmacéuticos de la Provincia de Buenos Aire
