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CHROMOSOME NUMBERS AND MORPHOLOGY 



IN TRIFOLIUM 



BY 

 HAAKON WEXELSEN* 



CONTENTS 



PAGE 



Introduction .. ..- - - 355 



Material and methods 356 



Chromosome numbers and morphology 357 



Chromosome numbers — 357 



Variations in chromosome size in the genus - 359 



Variations in chromosome size within the species 363 



Chromosome individuality -.. 365 



Attempts at species crossing 370 



Evolution of the chromosome complexes in Trifolium 372 



Summary 375 



Literature cited - 376 



INTRODUCTION 



The genus Trifolium is an outstanding genus within the family 

 Leguminosae. It contains a large number of species which show 

 great morphological variation and a wide geographical distribution 

 and includes several very important agricultural crops, such as 

 T. pratense, T. repens, T. hy~bridum, T. incarnatum, and T. alexan- 

 drinum. Although considerable plant breeding work has been carried 

 out, especially with T. pratense, no genetic analysis of any of these 

 species has been made and the cytological investigations are of very 

 recent date. The genetic analysis of other agricultural crop plants 

 has rendered important service to the plant breeder, and there is 

 every reason to assume that the same will be the case with the clovers 

 in which there are a large number of ''good" genetic characters. 

 It is of importance that the chromosome situation in these species 

 should be known before genetic investigations are started. The 

 results of the cytological investigations have been encouraging to the 

 geneticist and plant breeder as they show that in the most important 



* International Education Board Eesearch Fellow, Hjellum, Norway. 



