Abnormalities in avocado (Persea americana) ovules at blossoming are explained by demonstrating their possible origin at some stage of ovule development. Degeneration of the embryo sac at the micropylar site may occur at the four-nucleate stage or at egg-apparatus organization, prior to or after the filiform apparatus has formed. The time of occurrence of degeneration decisively determines the appearance of the degenerate remnants. The absence of an embryo sac and the presence of a double embryo sac originate at the earliest stages of the nucellar primordium; a third abnormality, compartmentalization, is assumed to originate at the megaspore tetrad stage.