Foram feitos estudos anatômicos sobre a organização e desenvolvimento dos meristemas axilares ortotrópicos de segmentos caulinares de Araucaria angustifolia cultivados in vitro, em meio básico de Murashigue & Skoog , sem reguladores de crescimento. Os resultados mostraram que estes meristemas formam àpices caulinares normais, razão porque pode-se esperar que plantas normais venham a ser obtidas a partir dos mesmos. Abstract Anatomy and aspects of the orthotropic axillary meristems organization and development of Araucaria angustifolia seedlings stem segments cultivated in Murashigue & Skoog’s basal medium without growth regulators were earried out. Provided that results showed normal shoots with normal apical meristem were developed from axillaxy bud rneristems, normal plantets and plants can be expected from in vitro stem segments cultivated on the cited conditions. Résumé Ètudes anatomiques sur l’organization et developement des méristémes axillaires des microboutures de jeunes plantes d'Araucaria angustifolia cultivées in vitro sur le milieu de culture de Murashigue & Skoog sans régulateurs de croissance. on áté realiseés. Les résultats montrent que cés mèristèmes forment bourgeans ou apex caulinaire normaux, raison por laquelle ont peut espérer plantets normaux dans les conditions citées.