309 



has been mollier — Ihe conlrary is improbable — give a bybiid 

 Ibat tbeorelically is most lii<ely lo i^el 14 + 28 = 42 chiomosomes. 

 Furlher, il' llie 14 </(illic(t-vhvQmosomes conjugale \\'\{h tho same 

 nuinl)er of chroinosomes iVom Ihe penlaploid lose, llicre theorcli- 

 cally ^viil be round 14 bivaleiil aiul 14 univalenl chiomosomes in 

 the diakinesis slage of the hybrid. I found precisely Ihis niimber 

 of gemini and singles in examining Ihe common while rose, ]i. 

 alba L., whicb is generally granled to l)e a hybrid l)ehveen (jdllicd 

 and (Inmetorum, Ihe laller being penlaploid. Not only Ihis one but 

 also Ihe other forms in my malerial delermined as hybrids behvcen 

 representalives of Ihe seclion Citninne and roses of olher seclions 

 have possessed Ihe Ihcorelically exi)ecled chromosome comi)inations. 

 Ibr inslance hihernicd [cdniiui x pimpinellifolia), cerlain forms of 

 involula (tomcnlosd x pimpinellifoUa), olher forms of involiitd ivillosd x 

 piwpincllifdUd', and cdnind x'pendiilii}d. 



19. A cytological examinalion, Iherefore, can be of use when 

 the hybrid origin of such roses is to be controled. 15y this melhod 

 it is also possible in cerlain cases, lo lind oul lo which group of 

 species the parenls of a hybrid belong (compare Ihe mt;o/;;/a-forms, 

 point 18). 



20. Though Ihe species of the seclion Cdninae have preserved 

 the jiower of sexual reproduclion, manifested \)y Ihe characler of 

 the lelrad divisions in the ovules and the anthers, by experiments 

 (Matsson), and the existence of numerous spontaneous hybrids, 

 they almost exclusively produce seeds in an apomictical way. This 

 kind of seed-formalion is experimenlally proved bj' Matsson, 

 Sch\s.euts(:hi,agi:i'., and others. The chromosome sets found are 

 a cytological proof. The mentioned comljinations of bivalent and 

 univalent chromosomes in e(jual mulliples of 7, slated in nearly 

 all my examined malerial of such roses, are namely not mainlained 

 in bushes originated from seeds which are produced in a sexual 

 way. I have examined some spontaneous hybrids betvveen forms 

 belonging to Ihis seclion, and I found in them very diverging 

 chromosome sets, the sporophyle numl)er being 32 — 86 and the 

 number of Ihe bivalenls ralher variable ilype 10, anorlhoploid forms), 

 This chromosome condilion is (]i\e lo Ihe mentioned dislurbances 

 in Ihe dislribution of the unpaired chromosomes in course of the 

 reduclion divisions. 



21. From the preceding point follows, that a bush belonging 

 lo the section Caninae and not having bivalent and single chro- 



