[Morphology and anatomy od the development of the anthocarp and fruit of Pisonia aculeata L. (Nyctaginaceae)].

Pisonia aculeata L. is a widespread species that occurs frequently in tropical and subtropical forests in the South of Brazil. This paper presents a morphological and anatomical study of the development of its anthocarps and the fruits. Flowers in pre and post anthesis and fruits in different stages of development were collected in the Horto Florestal of Maringá, Paraná State, Brazil. The anthocarp originates in the perigone and it can be characterized by the presence of an uniseriate epidermis on the abaxial surface, presence of glandular emergences, a glabrous epidermis on the adaxial surface and a parenchymatous mesophyll. This last tissue presents a great number of cellular strata due to the action of a ventral meristema installed still in the perigone phase. The pericarp develops from the wall of the ovary. The ovule is anatropous, bitegmic and crassinucellate. The mature seed presents a thin testa with thickened cell walls just in the rafe region, perisperm and endosperm with nuclear origin, without development of tegmen. The anthocarp has great importance in the process of dispersion of this species (epizoochory). This study confirms that the fruit is an achene and not a caryopsis as affirmed in the literature.