The embryology of diploid and polyploid Nigritella species is describe
d. The development of the adventitious embryos of the polyploids in re
lation to the sexual embryos of the diploids has been given special co
nsideration. Partial sexuality in the apomictic N. nigra has been prov
en for the first time by chromosome counts in proembryos after pollina
tion of a tetraploid plant with pollen from a diploid species.