The cytoplasmic DNA in generative cell and its behavior during spermatogenesis in Populus tomentosa, P. tomentosa × P. bolleana, P. alba × P. glandulosa and P. davidiana were observed by laser confocal microscopy with 4’,6-diamidino-2-phenylindole (DAPI) and 3,3’-dihexyloxacabocyanine iodide (DiOC). The results showed that the organelle DNA was not present during different stages of generative cell and sperm cell, which provided cytological evidence of potential maternal inheritance in section Leuce. The mitochondria were still present, but their DNA gradually degenerated and disappeared during pollen development. Consequently, the transmission of paternal mitochondrial DNA was interrupted, producing maternal inheritance of mitochondria. Meanwhile, relatively later elimination or degeneration of some plastids and their DNAs were found in P. alba × P. glandulosa. Finally, mitochondrial genetic mechanism in angiosperms was also discussed.