The Origin of Crepis and Related Genera 31 



been possible to work out with greater accuracy the classifica- 

 tion of species into groups within each subgenus, and to ascertain 

 phylogenetic relations. Figure 7 shows the genoms of ten Eu- 

 crepis species which provide a fine illustration of marked speci- 

 fic differentiation without any gross chromosomal alterations. 

 The five species represented in the left column are perennials, 

 and the others are annuals. Among the perennials, gymnopus 

 of Japan, praemorsa of Russia, and incarnata of southern Europe 

 are more similar to one another morphologically than to Eigiana 

 and Reuteriana of Syria. The two latter species are closely re- 

 lated, and very different from palaestina, pulchra, and pterothe- 

 coides, which occur in the same region. In fact, the three species 

 last named have in the past been referred to three different 

 genera, Cymboseris, Phaecasium, and Crepis. Yet comparative 

 morphology reveals the close relationship of palaestina and pul- 

 chra, and establishes that pterothecoides, although most preco- 

 cious and short-lived and very distinct from the other annuals, 

 also belongs in this group. Of the two remaining annuals, 

 granatensis is a very close relative of pulchra and occurs locally 

 within the range of this widely distributed species, and Sto- 

 janovii, an endemic of Bulgaria, is quite as distinct as pterothe- 

 coides, although obviously related to pulchra. This group there- 

 fore includes widely distributed and highly diversified species, 

 yet the chromosomes throughout are very similar in appearance. 

 Other such groups exist not only in Eucrepis but also in both the 

 other subgenera. 



These groups of related but well-differentiated species, with 

 very similar chromosomes among the species in each group, are 

 significant in several ways. For one thing, they prove that close 

 similarity in the chromosomes is direcdy correlated with close 

 taxonomic relationship in Crepis. They also indicate that the 



