304 



these are Ihe lirsl cases of pentaploidy foiind in spontaneous plant 

 species. Hexaploidy according to the formula 7 paired plus 28 

 single = 42 chromosomes was stated in glutinosa '•'libanotica, zarjra- 

 biense, Klukii, jiinzilliana, Dingleri {commonly assigned io junzilliana), 

 and a form of slijlosa. In two species, classilied in the seclion 

 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 Rosenberg (Svensk Bot. Tidskr. 1909) examined 

 forms from Hortus Bergianus belonging to canina and glaiica, 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 condilion 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. Bolh types, especially the divisions in 

 the embryo-sac mother cells, dilTer 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) Tiie 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 b). 



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 



