306 University of California Publications in Agricultural Sciences [Vol. 2 



Crepis biirsifolia, taraxaci folia, tedorum, hlattarioides, and aspera 

 might all be derived from capillaris by duplication of the intermediate 

 pair of chromosomes. 



The five-pair species listed below, although generally rather similar 

 in chromosome individuality, show certain distinct differences. 



Total 

 length 



aurea 21.0 18.0 16.2 15.1 13.2 161.9 



alpina 26.2 21.3 14.5 13.1 12.2 174.6 



foetida 25.0 20.8 17.7 15.8 14.4 187.4 



rubra 29.4 23.9 18.5 16.2 14.9 205.8 



Aurea (fig. 13) is outstanding since it lacks a long chromosome of 

 about twenty-five units. The figures are excellent, so that the averages 

 must be considered as very nearly accurate. Aurea is also very dis- 

 tinctive morphologically. Alpina (fig. 14), foetida (fig. 15), and rubra 

 (fig. 16) are much more alike in chromosome individuality. Alpina 

 seems to have three pairs resembling the shortest chromosome of 

 capillaris, and to be cytologically very like it otherwise. 



capillaris 26.2 20,4 14.8 



14.5 + 13.1 + 12.2 

 aljrina 26.2 21.3 = 13.2 



+0.9 -1.6 



Foetida might also have three duplicates of the shortest chromosome 

 of capillaris. 



capillaris 26.2 20.4 14.8 



17.7 + 15.8 + 14.4 

 foetida 25.0 20.8 = 15.9 



-1.2 +0.4 +1.1 



The figures for rubra compare better with those of capillaris if we average 

 the two intermediates and the two shortest together. 



capillans 26.2 20.4 14.8 



23.9 + 18.5 16.2+14.9 



rubra 29.4 = 21.2 = 15,5 



2 2 



+3.2 +0.8 +0.7 



It was noted above that Rosenberg (1918) suggested that probably the 

 small chromosome of capillaris had been duplicated twice for rubra. 

 It will be seen from the figures that duplication of the intermediate 

 and of the short chromosome appears more probable on the basis of 

 the measurements presented here. 



