A Preliminary Note on the Pollen Development of Lathyrus Odoratus

1. In this paper the main points in the pollen development of Lathyrus odoratus are briefly described. At the beginning of the meiotic phase the reticulum contracts from the nuclear membrane and exhibits an entirely granular appearance. 2. During thread formation, occasional amœboid nucleoli are observed. Nucleolar "budding" is also seen. 3. Connecting strands are constantly found between the synizetic knot and the nucleolus. 4. The thread at all stages appears usually to be a continuous structure. 5. The synizetic knot is followed by a stage in which the thread is thrown into seven definite loops which radiate out from the centre of the nucleus. For this stage, which has frequently been called the second contraction stage in cytological literature, the name broxonema is proposed. 6. The haploid number of chromosomes in Lathyrus odoratus is seven. Each loop represents one pair of homologous chromosomes joined distally end to end. 7. The arms of each loop are twisted round one another at one period. This affords opportunity for exchange of segments of chromosomes, and gives a possible physical basis for crossing over in a telosynaptic form. 8. These stages are followed by typical diakinesis and heterotypic divisions. 9. During homotypic telophase evanescent cell plates occur between the daughter nuclei. Later, the cell walls are formed by furrowing. 10. The tapetum remains uninucleate throughout.