28 E. B. Babcoc\ 



very small or highly specialized fruits. The basic, primitive dip- 

 loid number is lo and there are three 5-paired phylogenetic lines, 

 one in each subgenus. Furthermore, the subgenera are not sepa- 

 rated by fixed limits. From the peculiarities of certain species, it 

 is clear that Catonia tends to merge into Eucrepis, and Eucrepis 

 into Bar\hausia. Hence it seems highly probable that the three 

 lo-chromosome lines, one in each subgenus, had their origin in 

 a common nexus. At any rate, the genus must be accepted as a 



natural unit. 



The chromosomes of Crepis species are of three distinct types, 

 namely, those with a subterminal spindle-fiber constriction, those 

 with a subterminal constriction and bearing a trabant or satellite 

 attached to the proximal arm, and those with an approximately 

 median constriction. By comparing total length and relative 

 length of the proximal and distal arms, chromosomes of the first 

 general type are subdivided into classes designated A, B, and C, 

 the satellite-bearing chromosome is called D, and the small 

 median-constricted chromosome, E.^ One exception to this gen- 

 eral scheme occurs in a few species of Eucrepis in which the 

 largest chromosome has a median constriction, but there are 

 good reasons for considering this chromosome a modified A 

 type. Every simple diploid species of Crepis has only one pair 

 of satellite-bearing chromosomes. This fact alone often makes 

 it possible to recognize secondary or derived species from the 

 regular presence of more than two D chromosomes in the 

 somatic cells, even without a complete analysis of the whole 

 complement. 



All the lo-chromosome species of Crepis have one pair each 

 of chromosome types A, B, C, D, E. Just as 10 is the most primi- 

 tive number in the genus, so this combination of five types must 

 be considered the basic genom (haploid complement of a diploid 



