MEIOSIS IN TWO SPECIES AND THREE 



HYBEIDS OF CREPIS AND ITS BEARING 



ON TAXONOMIC RELATIONSHIP 



BY 



E. B. BABCOCK and J. CLAUSEN 



INTRODUCTION 



During the last few years certain species of Crepis have been used 

 rather widely in cytological investigations and to some extent in gen- 

 etical investigations as well. This has been due mainly to the low 

 number and the well marked individuality of the chromosomes in the 

 somatic nuclear plates. Crepis in these respects is a unique genus, 

 especially because the parentage of spontaneous hybrids in several 

 cases can be determined by the morphology of the chromosomes, as 

 has been shown by M. Navashin (1926, 1927a, h). 



The published investigations on the chromosome numbers of 

 Crepis have been mainly the work of Rosenberg (1909, 1918, 1920), of 

 the Berkele}^ group, summarized by Mann (1925) and by Babcock 

 and Lesley (1926), and of M. Navashin (1925, 1926, 1927). The last 

 mentioned author has specialized on the morphology of the chromo- 

 somes. Others who have contributed are Juel (1905), Tahara (1910), 

 Miss Digby (1914), and Marchal (1920). 



As the chromosomes of Crepis are especially satisfactory for 

 investigation during somatic divisions, most attention hitherto has 

 been paid to this phase. Rosenberg, however, investigated the divi- 

 sions during the formation of pollen mother cells; Navashin (1927i) 

 made some observations on the reduction division of C. capillaris X 

 C. aspera; while Lesley and HoUingshead have prosecuted a number 

 of (unpublished) investigations on the reduction division of certain 

 interspecific hybrids of Crepis. But no detailed study of the course 

 of the reduction division has been previously reported. 



The present study comprises the two species, Crepis aspera L. 

 and C. bursifolia L., together Math the three hj'brids: Crepis aspera X 



