The cytology of Brachycome lineariloba

Meiotic behaviour in PMC's and in ESMC's, the development of pollen and embryo sacs, and the chromosome constitution of endosperm in this species (species E) define its unique genetic system. It is not a normal diploid, and is perhaps best defined as a quasidiploid. — The somatic complement consists of a diploid set of four chromosomes plus a haploid set of two nonhomologous chromosomes. The latter are inherited solely via the pollen. — In meiosis in both PMC'c and ESMC's the two univalents divide at the first division and lag at second anaphase. Pollen grains which do not receive them are non-functional. The embryo sacs are of the normal Asteroid type, and each is derived from a chalazal megaspore. They do not transmit the univalent chromosomes. Following fusion of the polar nuclei and double fertilisation, the endosperm has a constitution of 14 chromosomes. — The system parallels the maternal inheritance of univalents in Rosa canina and in Leucopogon juniperinus, except that the univalents do not constitute a full haploid set, and except that their transmission is paternal.