The Origin of Crepis and Related Genera 49 



tate the recognition that gross chromosomal alterations have 

 played a more basic role, in the evolution of some o£ the higher 

 plants, at least, than has genie mutation. 



CREPIS 10.8 HIERACIUM 18 LACTUCA 18.16 



PRENANTHES 18 



INTERSPECIFIC HYBRIDIZATION AND 

 AMPHIDIPLOIDY (5+4X2=18) 



5-PAIRED AND 4-PAIRED SPECIES 



ORIGIN OF 8-CHROMOSOME SPECIES 



10 -CHROMOSOME PROGENIAL STOCK 



Fig. 12. Origin of the Crepidinae. The diagram illustrates the hypothesis that 

 the whole subtribe originated from a 10 -chromosome stock through: (i) origin 

 of 8-chromosome species by loss of one pair of chromosomes; (2) development 

 of Crepis from this group of 5 -paired and 4 -paired species; (3) origin of the 

 other genera through interspecific hybridization between some of those species 

 followed by amphidiploidy. 



A detailed discussion of various pertinent questions which 

 w^ill arise in the minds of critical readers must be postponed 

 until a future contribution. Let it suffice for the present to state 



