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mentioned Drosera*bastard, this irregularity proved to be merely apparent, as, dur*
ing metaphasis, 10 regularly formed gemini appeared in the equatorial plate, while
10 unpaired or single chromosomes were distributed over the spindle*figure. Start*
ing from Montgomery’s well*known hypothesis with regard to the chromosome*
pairing in the heterotypic division, the above*mentioned chromosome*arrangement
is thus explained: that 10 D. rotundifolia=chromosomes become paired with 10
D. longifolia, and the remaining longifoliatchromosomes constitute the 10 unpaired
ones. The result finally is the production of germ*cells of greatly varying chro*
mosome*numbers, as, of course, the unpaired chromosomes are distributed very ir*
regularly on the daughter nudei.
A large number of other cases with bastards of the type mentioned, x + 2x
or 2x + y, where y signifies a smaller number of chromosomes than x, has, later
on, been investigated by the writer in other species, and have proved to follow
the same Drosera=scheme.
By Mendel’s welbknown crossing*experiments with Hieracium=species, there
was discovered the remarkable faet that bastards were constant. The experiments
made, later on, by Ortenfeld showed that this depended on the occurrence of
apomixis or parthenogenesis in Fi and that the hybrids would segregate, when crossed
back with the parents. On the other hånd, Ostenfeld obtained, in some of his
crossing*experiments, a segregation already in Fi, for instance, in a single cross
between Hieracium auricula (sexual species) and H. aurantiaeum 29 hybrid indi*
viduals, all of which differed from each other. The writer has shown (1917) that
the germ*cells in one of the parent plants showed very different number of chro*
mosomes, which resulted in a greatly varying chromosome*arrangement in the
bastard individuals.
In the section Archieracium the sexual species have 9 chromosomes in the
germ cells; among the apogamous species the number of chromosomes in the
somatic nuclei is 27, thus proving, that these species must be considered as hybrids
between parent plants with 9, resp. 18 chromosomes in the germ*cells.
An interesting faet in Hieracum is, that the apogamous species of Pilosellae
are not absolutely apogamous but form both sexual embryo*sacs, which have
proceeded from a reduction*division, and embryo*sacs with the diploid number of
chromosomes, which have proceeded from a vegetative cell in the vicinity of the
sexual one, and displacing this latter during the course of its development.
A very peculiar circumstance was observed in the case of a bastard between
H. excellens and H. aurantiaeum where the germ*cells of the parent*plants have
each 18 gemini*chromosomes and a number of unpaired ones, while the bastard
in the heterotypic division shows over 22 gemini plus a number of unpaired
chromosomes. This depends thereupon, that some of the unpaired chromosomes
in each germ*cell are homologous and therefore form gemini. A similar condition
of things has also been shown by Holmgren (1919) in his important investigation
of genus Erigeron.
Of extreme importance is a newly published work by Täckholm (1920) on
the cytology of the genus Rosa. The purpose of that study was to learn to what
extent the use of cytological methods of research could be employed in the
elucidation of the problems that appear in the genus, distinguished by its enormous
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