Abstract

In this work is described the ontogeny of the orbicules in the anthers of Ilex paraguariensis. Anthers were fixed in glutaraldehyde and formaldehyde, post-fixed in osmium tetroxide and potassium ferricyanide, and embedded in Spurr's low viscosity resin. A modified Thiéry- reaction was used as a standard protocol contrast. The ultrastructural analysis of different stages of the anther development reveals (hat the pro- orbicules are formed in the periplasmic space of inner tangential and radial walls of the tapetal cells, during the tetrad stage. The pro-orbicules have an electron transparent core surrounded by an electrón dense orbicular wall. Later, after the dissolution of the tapetal cell walls, the orbicules grow in a fibrillar glycocalyx in the tapetum surface, on plasma membrane depressions. The orbicules in llex are synthesized in the extracellular medium only and must be homologous to the pollen grain ektexine.