Abstract: Using the squash method for chromosomes, cytological characters in pollen
mother cells (PMC) and pollen development traits of Larix principis-rupprechtii were
investigated. Our results showed that the PMC meiosis of L. principis-rupprechtii began in
autumn, remained at the diffuse diplotene stage through the dormancy of the plant during
winter and re-started the next spring to complete the process. It is mainly characterized by the
lack of synchronization of meiosis in the same anther and by the relatively quick processes of
every meiosis stage. After the re-start of meiosis, all the PMCs reached the tetrad stage within
three days. The main configuration of bivalents were rings caused by more than two
chromosome exchanges on the arms. Rod-bivalents produced by chromosome exchange on
only one arm were rarely observed in a few cells. The average configuration was
10.62II+1.38I. Of meiosis Metaphase II, there were patterns of parallel or perpendicularity,
forming eudipleural or tetrahedral tetrads, which are also the major tetrad types in the
monocots and dicots. After one week at the tetrad stage, callose cell walls started to dissolve,
then the four cells separated, and dispersed into the pollen cell, forming independent
single-nucleus pollen grains. Afterwards, the haploid nucleolus underwent further cycles of
mitotic division, resulting in the formation of five-celled pollen with two prothallial cells, one
tube cell, one stalk cell and one body cell.