Development of embryo and endosperm after intra-and interspecific pollinations in Rubus bellardi Weihe

Embryological features of seed sterility in facultatively apomictic Rubus bellardii (4x) were, in general, similar after intra- and interspecific pollinations, the latter with pollen of R. idaeus (2x) and R. caesius (4x). Apomixis seemed to have no influence on seed fertility. Some pistils stopped growing and the egg cells were unable to further development. Different stages of seed formation occurred within the same flower together with the retardation of egg cell division as well as the degeneration of egg cell, embryo and of endosperm. Endosperm was the last to degenerate and, being to some degree independent, it was able to reach the cellular state without embryo formation. A retardation of gametic fusion (sperm nucleus lying at a distance from the female one on the 5th and 8th day after pollination) might be connected with the parthenogenetic nature of the egg cell.