ANOMALOUS PROGENY 193 



Table 27 

 Polyploid Hybrids with Abnormalities of Chromosome Constitution 



Newton and Pellew, 1929. Primula kewensis {:\x) selfed. Seedlings, 2w = 20 



26. 

 Steere, 1932. Petunia axillaris {2x = 14) x P. hybrida {^x = 28). F^, 



all 2x. 

 Shimotomai, 1933. Chrysanthemum marginatum (io;>^ = 90) x C lavandula- 



folium {2x = 18). One seedling 8x. 

 Nishiyama, 1933. Avena fatua {6x = 42) X A. barbata {^x = 28). Fj, ^x ; 



Fg. 6a; ; F^ (one plant resembling A. strigosa) 2x. 

 Darlington, 1933. Prunus avium {2x = 16) X P. cerasus {^x = 32). Three 



seedlings 2x (Knight's hybrids). 

 East, 1934. Fragaria vesca {2x = 14) x F. virginiana {Sx = 56). One 



seedling 2x. 

 Karpechenko, 1935. Brassica oleracea, green {ix = 18) x {B. oleracea, red X 



Raphanus sativus, ^x). Progeny all 2x and heterozygous, red-green. 



Brassica oleracea {2X — 18) x {Raphanus sativus x B. oleracea, 4A-). 

 Progeny all ^x. 



Some of these abnormalities may be due to male parthenogenesis 

 or to irregular fusion of nuclei in the egg (cf. Bergman, 1935, on 

 Leontodon). Others may be related to unexplained abnormalities 

 of mitosis that have been occasionally found in polyploids (e.g., 

 Huskins, 1934). An explanation of others again may be found 

 perhaps in analogy with double fertilisation in echinoderms, which 

 leads to the formation of spindles with three or four poles and 

 hence to irregular reduction in the chromosome number (Boveri, 

 1907). In the Brassica-Raphanus hybrid, however, the nature of 

 the abnormality has been accurately defined by using red cabbage 

 for the parent of the tetraploid hybrid and green for the diploid. 

 The diploid progeny were heterozygous and were therefore true 

 crosses. The tetraploid hybrid which has Brassica as the female 

 parent therefore produced haploid Brassica pollen and hence 

 diploid offspring. On the other hand the tetraploid hybrids derived 

 from Raphanus as the female parent produce normal diploid pollen 

 and hence triploid offspring. 



The progeny were abnormal in being diploid only when Brassica 

 was the maternal parent of the first cross. Evidently the Raphanus 

 chromosomes were all lost at meiosis in the jp^. Presumably at 

 this stage there is an abnormal reaction between the Raphanus 

 chromosomes or their centromeres and the Brassica cytoplasm or 

 its spindle-determining agents. 



R.A. CYTOLOGY. 7 



