CHROMOSOME RACES IN CARDAMINE PRATENSIS IN THE 



BRITISH ISLES 

 By F. Hussein 



Botany Department, Cairo University 



Introduction 



Cardamine pratensis L. is a highly variable species in its morphological characters, 

 particularly in the type of flower. The prevailing type of flower is single, but some forms 

 occur bearing completely sterile double flowers, with all the floral parts, except the calyx, 

 petaloid. Another sterile double variant was recorded by Blackburn (1922) in which the 

 flower resembles that of the double form of Arahis caucasica in that each flower repeats 

 itself several times by a median bud ("Arabis type "). In 1923 she also noted, in Nor- 

 thumberland, the occurrence of a " semidouble " type, in which the ovary becomes 

 swollen and bursts into a double or an incompletely fertile flower. 



Early chromosome counts for the species were 2n = 32 and 2n 64 by Manton 

 (1932) for material collected from Cambridge and Southport respectively. Lawrence 

 (]93]) gives a count of 2n = 30 for material obtained from the grounds of the John 

 Innes Horticultural Institution. Flovik (1940) in his cytological survey of the Spitzbergen 

 flora listed the species among those found in the polyploid form only (2n = 64). Guinochet 

 (1946) recorded three chromosome numbers for material from the Jura Mountains : 

 2n = 16, 2n = 30 and 2n = 40. Lovkvist (1946) reported several counts for material 

 collected from Southern Sweden. These were : 2n = 30, 56, 60, 64, 68, 72 and 76 with 

 a few of 2n = 58 and 84. Banach (1950) gave a similar long list of numbers for Polish 

 plants. Howard (1948) gave counts of 2n = 56 for material collected from Cambridge 

 and Cheshire. The present author (1948), working on the chromosome numbers and 

 geographical distribution of the species in the British Isles, found only two chromosome 

 races : 2n 56 and 2n = 30. 



The distribution map given in 1948 included 70 plants and it showed the restriction 

 of the 2n = 30 plant to the south and the prevalence of 2n = 56 all over the country. My 

 request for more material brought the number of investigated plants up to 113, obtained 

 from 100 different localities, belonging to 31 vice-counties. The following account 

 contains a more complete distribution map, a cytological study of the chromosome races 

 and details of the relation between the different types of double flowers and the chromosome 

 numbers. 



Results and Discussion 



Geographical Distribution 



Of the total number of plants only 19 gave counts of 2n = 30, the rest of the material 

 having a complement of 2n = 56. No other chromosome race was found in the British 

 Isles by me. Recently Mr. D. E. Allen has suggested that the 2n = 64 count, originally 

 made by Professor Manton for a plant from the Southport dunes, represents a third 

 chromosome race which is readily distinguishable morphologically {Yearbook B.S.B.L, 

 1952, 56). The distribution map shows but one exception to the rule that the race with 

 single flowers and lower chromosome number is restricted to the south. The exceptional 

 plants were found in a wood in Northumberland in two different years. They may well 

 have been due to accidental introduction with young trees since Lilium martagon was 



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