In this paper the behaviour of sex-chromosomes during meiotic divisions in male and female plants of the wild hop, Humulus lupulus, var. cordifolius is described. The results are summed up as follows:- 1. The male has one tetrapatite chromosome in addition to 8 bivalents in the first meiotic division of pollen mother cells. The behaviour of the tetrapartite chromosome is similar to that of the sex-chromosome complex in Humulus lupulus (SINOTÔ, 1929). Therefore the constituent members of the chromosome are named X1Y1X2X2 respectively, counting from the large end member to the small end one. At the division, the tetrapartite chromosome arranges itself in a zigzag form in the spindle as Y1Y2 X1X2 and each member goes to its nearest pole. Consequently two kinds of pollen grains, one with X1X2 and the other with Y1Y2 are formed. 2. The female, however, shows 10 equally paired bivalents in the first meiotic division of embryosac mother cells. Judging from their size and form the largest rod bivalent seems to correspond to the X1X1-pair and the largest ring, to the X2X2-pair. As the result of regular meiotic divisions, megaspores have alike X1 X2. 3. From the above mentioned results, the chromosome formulae of zygotic and gametic nuclear phases in both sexes are denoted as follows: 2n pairing of chromosomes n _??_ 20=X1Y1X2Y2+16 Y1Y2 X1X2+8II X1X2+8, Y1Y2+8 _??_ 20=X1X1X2X2+16 X1II+X2II+8II X1X2+8 4. Chromosomes in root-tip cells were not studied, but fortunately in an abnormal pollen mother cell we met with 20 morphologically characteristic chromosomes which correspond to the diploid number. From the comparison of these chromosomes with those in the first meiotic division, we can assume that the X2 and Y1 are medianly, the X1 and Y2 submedianly, constricted large chromosomes and the remaining 16 autosomes are medianly or subterminally constricted ones in equal numbers.