In phyllotaxis of the majority of cactus genera, especially Mammillaria, Notocactus, Gymnocalycium, the main Fibonacci pattern predominates. In some genera, to which Rebutia and Aylostera belong, a broad phyllotactic spectrum with the accessory patterns prevailing, was discovered. The analysis of the sequential initiation of areoles in seedlings of both groups shows that in Rebutia, Aylostera, Pseudolobivia, Gymnocalycium areoles are initiated in pairs. The first pair is circumferentially positioned exactly as cotyledons, slightly above them. The subsequent pair arises at the right angle to the first pair. Later either the decussate arrangement of areoles develops or, after a small torsion of successively initiated pairs - the main bijugy. In some cases, due to the initial tricotyly, areoles similarly form either tricussate pattern or initiate the main trijugy. In Rebutia occasionally areoles of one pair differ in timing of their appearance or deviate from expected circumferential position indicating the change of the pattern into simple spiral. In contrast to these situations, areoles in Mammillaria are initiated not in whorls but separately, the first one between cotyledons. Successive areoles appear in a spiral sequence, quickly establishing low expressions of the main Fibonacci pattern. Despite the different modes of areole initiation, the reasons for the phyllotaxis diversity in such genera as in Rebutia are not completely elucidated since in seedlings only the most common patterns have been found. It is suggested that the diversity of patterns in cacti is due to subsequent ontogenetic transformations of phyllotaxis. These may involve qualitative change of patterns as commonly in Rebutia and ontogenetic increase of contact parastichy numbers of the main Fibonacci pattern as in Mammillaria.

Key words: Cactaceae, morphogenesis, pattern ontogenetic transformations, phyllotaxis