44 E. B. Babcoc\ 



two from Madeira and one from the Canary Islands. Several are 

 of rather wide distribution, while the tetraploid species con- 

 nected with them are more restricted and undoubtedly more 

 recent. It seems hardly necessary to go into further detail con- 

 cerning their distribution, as they are certainly connected with 

 Asia Minor and the Caucasus region. 



In general, the evidence on distribution of related groups of 

 Crepis species is wholly consistent with the assumption that the 

 center of origin and distribution for the genus is in south-central 

 Asia. It follows, then, that there was subsequent migration to 

 the west, with the development of secondary regions of specia- 

 tion in Asia Minor, the Balkan Peninsula, the European Alps, 

 Abyssinia, and the Mediterranean littoral, and to the northeast, 

 with secondary centers in the Altai region, northeastern Asia, 

 and northwestern America. Although there are still many in- 

 teresting problems to be solved with reference to specific rela- 

 tions and the nature of endemics,— concerning whether they are 

 epibiotic or of recent origin,— the most fundamental problems 

 may be considered as solved with the establishment of the center 

 of origin in southwestern Asia and with the conclusion that 5 

 and 4 are the basic haploid chromosome numbers in Crepis and 

 that 5 is the more primitive number. 



Origin of the Crepidinae 



What bearing have these conclusions on the problem of origin 

 in the Crepidinae? It is impracticable to give a detailed study of 

 distribution in Hieracium, Lactuca, and Prenanthes, but it can- 

 not be without significance that in each of these genera south- 

 central Asia is centrally situated with reference to generic limits 

 of distribution (fig. i). Furthermore, the species of that unique 

 smaller group, the Glomeratae, which show affinity for both 



