Karyological Studies on Osmundaceae II

The karyotypes of three Japanese species of Osmundaceae: Osmundastrum claytonianum, Os. Cinnamomeum var. fokiense and Plenasium banksiifolium, were investigated. The somatic chromosome numbers of the three species were found to be 2n=44. The chromosome complements of the species in Osmundaceae so far studied by the authors can be divided morphologically into 6 (A-F) groups, and possess approximately similar karyotypes except for one pair of the submedian chromosomes in the B-type (Fig. 6). Judging from the karyotypes, the primary basic number of chromosomes in Osmundaceae can be considered to be x=11, and thereby many species in Osmundaceae, which possess chromosomes 2n=44, can be considered to be tetraploid.