NOTES ON CAREX FLAVA AND ITS ALLIES 



III— THE TAXONOMY AND MORPHOLOGY OF THE 

 BRITISH REPRESENTATIVES* 



By Elizabeth W. Davies 



University College of Leicester 



This group of closely related species included in the section Extensae of the sub- 

 genus Carex is represented in Great Britain by :- C. flava L., C. lepidocarpa Tausch, 

 C. demissa Hornem., C. serotina Merat, C. scandinavica E. W. Davies (E. W. Davies 

 1953a). These species have for many years caused difficulty and been the subject of 

 much misidentification. And although certain characters have been found useful for 

 distinguishing the species, and their nomenclature has been elucidated (Nelmes 1945, 

 1947; Wiinstedt 1947; Senay 1950; Tutin 1952; and Davies 1953a and b), no detailed 

 taxonomic or ecological study had been made, and no cytogenetical survey carried out. 

 For this reason an investigation of this kind was begun, and the biometric and morpho- 

 logical aspects of the problem will be briefly discussed here. A key to the European 

 members of this group and C. viridula Michx. is given opposite. 



A range of forms of each species was collected from as many different localities as 

 was possible. These plants, after their chromosome numbers had been determined, were 

 planted out in an experimental garden, where conditions were as uniform as possible, so 

 that any effects of differences in the environment on the phenotype were to a great extent 

 eliminated ; and the genotypes of the individuals and species could be compared directly. 



These transplant experiments have shown how much variation within the species is 

 due to environmental conditions. As was to be expected, certain characters, such as 

 absolute size of the plant and its vegetative organs, have proved to be subject to con- 

 siderable phenotypic modification, while in contrast the floral parts appear to be much 

 more constant. The main morphological study, and detailed measurements given in 

 Table 2, have been made on herbarium specimens gathered from the same plants in 

 the field. 



1. Height 



On the whole this has proved an unreliable character, as much variation in height 

 and size is found not only between plants of the same species from the different habitats, 

 but also in the same plant during one year, and in successive seasons growing in the 

 same locality. Thus, C. serotina, seen at Wicken Fen, Cambridgeshire, in August 1951, 

 had fertile stems ranging from 2-25 cm. on one plant. This species at Frensham Pond, 

 Surrey, had shoots 25 cm. long in July 1951, while in the same month in 1952 these plants 

 were very dwarf and the fertile stems were only 2 cm. in length. 



This variation in absolute size of the plant from season to season, and from different 

 localities, can usually be correlated with a change in ecological conditions, as after they 

 had been grown under uniform conditions for two years they showed very much less 

 range of size. 



Although there is considerable variation, it is possible to make some general state- 

 ments about height. C. flava is normally the tallest member of the group, and the 



• Part of a thesis approved lor the degree ul Ph.D. by the University of London. 



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