CHROMOSOME RADES IN CARDAMINE PRATENSIS 171 



found in the same wood and its presence certainly suggests planted, rather than natural, 

 woodland. For the same reason — planting — the northern localities of the 2n = 30 sterile 

 doubles may not be significant as most of them were from gardens. The northern and 

 wider distribution of the 2n = 56 race and the virtual restriction of 2n = 30 to the 

 southern unglaciated regions of Britain may furnish another example of a polyploid 

 race able to invade new regions in which its diploid relation cannot survive. 



Cytological Differences 



The 2n = 30 plants had either a single, sterile double, or "Arabis type " flower. A 

 comparison between the somatic chromosome complements of the three types did not 

 show any obvious differences either in shape or in size of chromosomes (Fig. 1 a). Among 

 members of the same complement shape and size differences were few. In length the 



