1. In the present investigation seven hypo-tetraploid garden varieties of Hyacinthus orientalis were studied karyologically, of which the chromosome numbers of Amsterdam (2n = 30), Colosseum (2n = 30) and Carnegie (2n = 29) were determined for the first time.
2. The karyotypes of seven varieties studied can be L0rmulated as follows :
Garden varieties Karyotypes
Mr. Dames 2n = 31 = 16V+15J
Dr. Stresemann 2n = 31 = 16V+15J
Delft Blue 2n = 30 = 15V+15J
Myosotis 2n = 30 = 15V+15J
Amsterdam 2n = 30 = 16V + 14J
Colosseum 2n = 30 = 16V+ 14J
Carnegie 2n = 29 = 16V + 13J
The various garden varieties of Hyacinthus orientalis studied by the author (series I - V) can be divided into diploid (2n = 16), triploid (2n = 24), hyper-triploid (2n = 25-28) and hypo-tetraploid (2n = 31 -29), moreover among the varieties in the same ploidy a slight morphological differentation of chromosomes was observed.