242 



THE BEHAVIOUR OF POLYPLOIDS 



together with a haploid set of A^. sylvestris (2x = 24), a plant was 

 derived in Fg having fifty chromosomes forming 2a; + i pairs 

 (Webber, 1930). Secondly, from a cross with the diploid A^. rustica 

 a new race with 30 bivalents has been derived (Lammerts, 1932). 

 Thirdly, from the cross between the probably autopolyploid Crepis 

 biennis (2n = 40 = 8x) and the diploid C. setosa (zn = 8) it has 

 been possible, owing to autosyndesis, to derive a new true-breeding 



Table 40 

 Observations of Secondary Pairing at Meiosis 



A. Simple Polyploids. 



Dahlia variabilis {8x = 64) 



Prunns cerasus {4X = 32) . 



P. domestica X P. cerasifera {4X = 32) 



P. Laurocerasiis {22x — 176) 



Primula kewensis {4X = 36) 



Digitalis mertonensis {i6x = 112) 



Veronica spp. {4X — 68) 



Solanum tuberosum {2x = 24) 



B. Secondary Polyploids. 

 Pyrus Malus {4X -\- 6 = 34) 



CratcBgus, Mespilus, Cotoneaster, etc. 



(-/^ + 6 = 34) 

 Dahlia Merckii {4X + 4 — 36) . 

 Acer platanoides {4X + 2 = 26) . 

 Oryza sativa {4X + 4 = 24) 

 Empetrum nigrum {4X + ? = 26) 

 E. hermaphroditum {8x -f- ? = 52) 



Brassica Napus {2n = 36) 



B. rapa {2x + ? = 20) 



B. oleracea (2X + 6 = 18). 



Dicentra spectabilis {2X + 2 = 16) 



C. Between Univalents. 

 Nicotiana . . . . . 

 Taraxacum . . . . . 



Kuwada, 1910 ; Lawrence, 1929, 



1931- 

 D., 1928. 

 D., 1930. 

 Meurman, 1929. 

 Newton and Pellew, 1929. 

 Buxton and Newton, 1928. 

 Graze, i935- 

 Miintzing, 1933. 



D. and Moffett, 1930 ; Heilborn, 

 1935- 



Moffett, 1931, 1934. 



Lawrence, 1929, 1931. 



Meurman, 1933. 



Sakai, 1935. 



Hagerup, 1927 ; cf. D., 1931. 



Hagerup, 1927 ; cf. D., 193 1 ; 



Wanscher, 1934. 

 Catcheside, 1934. 

 Catcheside, 1934. 

 Catcheside, unpub. 

 Matsuura, 1935. 



Lawrence, 1931. 

 Gustafsson, 1934, i935- 



form, Crepis artificialis, having ten pairs of chromosomes from 

 C. biennis and two from C. setosa {cf. Table 30). This new form is 

 balanced in its biennis fraction, unbalanced in its setosa fraction 

 (lacking 2 pairs of chromosomes). It therefore has the constitution 

 of a secondary polyploid. 



All these new forms are capable of breeding true, yet they differ 

 in genetic balance and external form from their progenitors. 



