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304
these are the first cases of pentaploidy found in spontaneous plant
species. Hexaploidy according to the formula 7 paired plus 28
single = 42 chromosomes was stated in glutinosa *libanotica, zagra-
biense, Klukii, junzilliana, Dingleri (commonly assigned to junzilliana),
and a form of síylosa. In two species, classified in the section
Caninae, were found 14 instead of 7 paired chromosomes, namely
in britzensis (14 paired plus 7 singles — 42, type 8) and omissa (14
paired plus 14 singles = 42, type 9). —
10. The two by RosENnEnG (Svensk Bot. Tidskr. 1909) examined
forms from Hortus Bergianus belonging to canina and glauca, in
which he found usually 7 bivalent and about 20 unpaired chromo-
somes, have 7 paired and 21 single.
11. As it will be seen from the above mentioned, the species
stylosa, rubrifolia and junzilliana which have been much discussed
from the systematic point of view show quite the same peculiarity
regarding the chromosome condition as the other Caninae.
12. All these to the section Caninae belonging species agree,
moreover, perfectly as to the behaviour of the chromosomes du-
ring the reduction divisions. Indeed, the divisions in the pollen
mother cells and in the embryo-sac mother cells are carried out
in a quite different way. Both types, especially the divisions in
the embryo-sac mother cells, differ in certain respects from other
types of chromosome distribution found in plants.
In the pollen mother cells of a pentaploid rose, for instance a
canina, 7 bivalent and 21 single chromosomes will be recognized
during the diakinesis (fig. 2 a). The following reduction division
is carried out with great precision by certain times:
1) The bivalents pass to the equatorial plate, the unpaired are
irregularly scattered on the spindle (fig. 1 a).
2) The single chromosomes pass to the equatorial plate. They
are arranged in the same plane as the bivalents and surrounding
them (figs. 1 b and 2 D).
3) The partners of the bivalents pass to the poles, while the
singles still remain in the equatorial plate, where they undergo
segmentation (fig. 1 c).
4) ’The members of the pairs having already reached the poles,
the halves of the singles separate and begin their journey towards
the poles (fig. 1 d).
There are then two different anaphase stages, that of the biva-
lents and that of the unpaired chromosomes. Not all the halves
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