Archive image from page 7 of Cytological studies of five interspecific. Cytological studies of five interspecific hybrids of Crepis leontodontoides cytologicalstudi65aver Year: 1930 140 University of California Publications in Agricultural Sciences [Vol. 6 enees between the chromosomes are not evident, espe- cially since the D-chromosome loses its satellite in the hybrid. The D-chromosome of tectorum retains its satellite unaltered, but in no case was a satellite found on the leontodontoides chromosome, a phenomenon (amphiplastie) which seems to be characteristic of certain i
Archive image from page 7 of Cytological studies of five interspecific. Cytological studies of five interspecific hybrids of Crepis leontodontoides cytologicalstudi65aver Year: 1930 140 University of California Publications in Agricultural Sciences [Vol. 6 enees between the chromosomes are not evident, espe- cially since the D-chromosome loses its satellite in the hybrid. The D-chromosome of tectorum retains its satellite unaltered, but in no case was a satellite found on the leontodontoides chromosome, a phenomenon (amphiplastie) which seems to be characteristic of certain inter- specific hybrids as first described by Navashin (1928). Figure 3 shows a somatic plate in which the differences between the two haploicl sets are evident, and each of the chromosomes from the two parents may be identified. Fig. 3. Somatic metaphase of Ft C. leontodontoides-tectorum. Meiosis With such morphological differences between the parental chro- mosomes, there is little reason to expect conjugation of the chromo- somes of the two species at the meiotic divisions in the hybrid. Ac- cordingly, at diakinesis and metaphase of the first meiotic division the nine chromosomes of the hybrid are frequently unpaired. In figure 4a a diakinesis stage shows nine unpaired units of which the four larger tectorum chromosomes are distinct from the five smaller and rounder leontodontoides chromosomes. Occasionally a stage im- mediately following the disappearance of the nuclear membrane shows the nine units arranged in a semicircular fashion, suggesting a telosynaptic arrangement (fig. 4&). Where no pairing has occurred up to diakinesis, there is apparently little tendency for the formation of a definite first metaphase plate. Thus a scattering distribution of the nine unpaired chromosomes (fig. 4c) seems to follow directly upon such a late diakinesis as that shown in figure 4b. Rarely a I-M is seen in which all the nine units are rather definitely arranged in an equa- torial pla
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