Abstract
Abstract Callose walls in sporogenesis of <Biota orientalis> Endl. First observations. — Formation of callose walls during micro and megasporogenesis in Biota orientalis Endl. has been studied. After the end of the first prophase, the pollen mother cells are envelopped by a double layer of callose; when the tetrads are formed, further callose is laid down between these, isolating each of them from the others, while the callose wall of the mother cell keeps them together. Later, the callose is destroyed and the young microspores become free in the cavity of the microsporangium. The isolation of microspores, already reported for other Gymnosperms and Angiosperms, should prevent genetical influence of the spores upon their sisters. During megasporogenesis, a layer of callose has been observed in Biota orientalis around the upper cell of the dyad. This formation had been reported, up to now, for only one Gymnosperm, Encephalartos; it had been interpreted as an evolution relic of a mechanism isolating the spores in the sporangium. Since in megasporogenesis and embryogenesis of Biota other ancestral characters are found, probably the callose wall presents a phylogenetic interest.
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