174 



F. HUSSEIN 



(4) The distribution map supports the conclusion that the 2n = 30 race is almost 

 restricted to the southern unglaciated part of the country, and thus suggests the superiority 

 of the 2n = 56 race in invading new territory. 



(5) A cytological comparison between the two races indicates that there is not 

 sufficient evidence to determine the type of polyploid relationship between them. 



(6) Doubleness of flower in both races is thought to have a genetical cause. In 

 the 2n = 56 race some unknown physiological factor may render it capable of setting 

 seed. Both the cytological aspect and the subject of the physiological control of semi- 

 doubleness are in need of further investigation. 



ACKNOWLEDGM ENTS 



I am indebted to Professor M. Thomas and Dr. K. B. Blackburn of the Botany 

 Department, King's College, Newcastle-upon-Tyne (University of Durham) for their 

 unfailing interest during the progress of this work and to all those, too many to mention, 

 who have generously supplied me with living material. 



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BLACKBURN, K. B., 1922, Notes on peculiarities found in the Cuckoo Flower, The Vasculum, 8, 133. 



, 1923, Another abnormality in Cardamine pratensis. The Vasculum, 9, 109. 



FLOVIK, K., 1940, Chromosome number and polyploidy within the flora of Spitzbergen, Hereditas, 26, 430. 



GUINOCHET, M., 1946, Sur I'existence dans le Jura Central de races ecologiques aneuploides et poly- 

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HUSSEIN, F., 1948, Chromosome Number of Cardamine pratensis. Nature, 161, 1015. 



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