1) The basic number of chromosomes of Paris quadrifolia L. var. obovata REGEL et TIL. is 5, and its 5 chromosomes, which were designated as a, b, c, dT (or do), and e, are easily distinguishable by their relative lengths, positions of constrictions and presence or absence of a trabant (Figs. 1-2). 2) The original form has a, b, c, dT, and e chromosomes all in pair in its somatic complement (the suffix T means the presence of a trabant): aa+bb+cc+dTdT+ee=10 (2rom) (Figs. 1-2) In the secondary diploid form one of its d type chromosome pair is deprived of its trabant, which may be designated as. do chromosomes (cf. Figs. 8-12). Accordingly its somatic complement is as follows: aa+bb+cc+dTdo+ee=10 (2rom) The triploid form described here comprises triple complement in its somatic cells, but two of its three d type chromosomes are do's (cf. Fig. 4): aaa+bbb+ccc+dTdodo+eee=15 (3rom) 3) Though their mother chromosomes were undeterminable, chromosome fragments in pollen mother cells and pollen grains were observed even in diploid forms (Figs. 5-6). Rest of connecting filament were frequently observed at mitosis in pollen grains and in somatic cells (Figs. 9-10). dT, and do chromosomes conjugate at meiosis in diploid and also in triploid (Figs. 3-4). Other Paris species (P. tetraphylla A. GRAY and P. japonica FRANCH.) have not such a d type chromosome (cf. Haga 1934). Thus it is very probable to consider that dT type has transformed into do type through the fragmentation at the region of connecting filament of trabant, and that the present triploid is an autotriploid form. 4) Although a diploid form containing do chromosome pair has not been found as yet, if we presume that such combination is not lethal, dTdo type might have arisen directly from dTdT type or through the. cross between dTdT and dodo type; dodo type from dTdT or dTdo. Furthermore, there is possibility to arise from the cross between them. And the present triploid might have arisen through the various combinations of gametes of the above three diploid types with the exception of the selfing of dodo type, in these cases, one side of the sexes is considered as the unreduced diploid gametes. 5) Diploid form containing dT and do chromosome produces two kinds of pollens differing in their d type chromosomes. i.e. containing dT or do, approximately in equal number (Figs. 7-8). Chromosome numbers and combinations in pollens of triploid form are various (cf. Formulas at page 183). Among the great majority of pollens, haploid, diploid and triploid pollens having 1, 2, and 3 basic complements will be expected, and in reality such pollens were observed (Formulas 1, 7, and 8 at page 183). Various combinations of such polyploid gametes will result in 2n-6n autopolyploid plants, and various polysomic plants will be arisen from certain polysomic gametes. 6) The cross 3rom×2rom produced some seeds various in size even within a berry. This probably indicates that certain eggs differing from the ordinal haploid eggs had functioned (Fig. 13).