The genomic DNA content of a cultured cell of Marchantia polymorpha HYA-2F was examined using a flow cytometer. It was estimated to be 0.32 pg (C), with a G+C content of 57.1%. The DNA content was less than that of Arabidopsis thaliana. The frequency of transformation by Agrobacterium tumefaciens using a binary vector plasmid pBI121 in the presence of acetosyringone was approximately 10%. GUS expression analysis and Southern blotting analysis of the genomic DNA of transformants revealed that all regions of T-DNA on plasmid pBI121 were integrated into the genome of M. polymorpha.