Abstract
In the present study the chromosome number of 25 Clematis species, hybrids and horticultural forms is given. One of them was tetraploid, 2n=32, one hexaploid, 2n=48, and the rest diploids with 2n=16.
The karyotypes of twenty-two of these Clematis forms were analysed more or less in detail, and it was found that the diploid chromosome complements were in every case very uniform. In all of them the following chromosome-types could be distinguished: five pairs of V-formed chromosomes viz. A, B, C, D, and E, the subterminally constricted F pair and the G and H pairs with an almost terminal constriction. The two lastnamed ones being generally provided with a satellite. In the tetraploid C. mandschurica and the hexaploid C. paniculata a corresponding number of different types was present.
In five plants the satellite chromosomes were heteromorphic, and indication of amphiplasty was observed.
Ten of the Clematis forms studied were inversion heterozygotes is respect to one or more inversions. In consequence hereof during the reduction divisions chromatid bridges, fragments and other irregularities, as for instance univalents and lagging chromosomes, appeared.
A special attention was paid to the relation between the structural changes and the fertility of the plant. It could be stated, that in forms with a pronounced structural hybridity the pollen was bad and that these forms therefore could be propagated only asexually. The amount of such chromosomal alterations and the grade of fertility are in Clematis, comparably to that in tulips, in a reversed relationship to each other.
