The diploid number of chromosomes in the male plant is 17 and in the female 16.
Of the 17 chromosomes in the male, 14 are autosomes and the remaining 3 sex-chromosomes. The sex-chromosomes are almost equal in size and they are larger than the largest autosomes.
There are two V-shaped large X-chromosomes in the somatic division of the female plant, while only one such chromosome beside 2 large J-shaped ones (Y
1 and Y
2) can be found in the male.
The sex chromosomes form a tripartite complex in the reduction division of the pollen mother cell. The X-element in the middle of the tripartite chromosome goes to one pole and the Y
1 and Y
2 attached to both ends of the X pass to the other.
The sex-chromosome complex is not a simple XY pair as first described by WINGE (1923). Such a figure (Fig. 3), from which WINGE drew his conclusion, is only a transitory form to the V-shape arrangement (cf. KIHARA 1927. P. 442). The behavior of the tripartite sex-chromosomes in
Humulus japonicus is, therefore, quite identical iwthht atof corresponding stages in
Rumex acetcsa.
WINGE'S figures (Fig. 11 and 12) representing diakinesis of a pollen mother cell and 16 chromosomes of an archespore mother cell are quite in accordance with my observations.
The chromosomal formulæ of the plant are as follows:
diploid haploid
_??_ 14+Y
1+X+Y
2 7+X, 7+Y
1+Y
2_??_ 14+X+X
The diploid number of chromosomes in
Humulus lupulus (_??_) is 20.
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