338 University of California Puhlications in Agriculturul Sciences [Vol.2 



but the relative importance of size and shape as indicators of relation- 

 ship between species can be tested only by species-hybridization and 

 jjenetic analysis. Probably botli modes of attack will sometime prove 

 useful, but thus far they have not given us clues to relationship which 

 could not be determined by comparative length alone. Our material, 

 like that of Nava-shin, shows Trahanten attached to the shortest chro- 

 mosome in both tectorum and Marschcdlii, species which are widely 

 se]iarated in all classifications. This is very disappointing, since one 

 might have hoped that they could be differentiated thereby. It seems 

 evident from our studies that if Navashin were to make comparative 

 measurements of the chromosomes, he might change his estimate of the 

 chromosome homologies in the species which he studied. 



Corrections in Nomenclature in Part I 



In the preceding paper (Mann, 1925), the following corrections 

 should be made : 



For hreviflora Delile read senecioides Delile. 



For grandifiora Tauseh read conyzaefolia (Gouan) Dalla Torre. 



For Sieberi Boissier read montana d'Urville. 



SUMMARY AND CONCLUSIONS 



1. Taxonomically considered, the genus Crepis, as it stands at 

 present, is a heterogeneous assemblage of distinct but related groups of 

 species. The sections recognized by Hoffmann and tlieir classification 

 by him are not wholly satisfactory on the basis of comparative morph- 

 ology alone. A more satisfactory classification of the species under 

 consideration, which reduces the sections from eleven to ten and 

 regroups certain species, is suggested, and the cytological evidence is 

 considered in relation to the new grouping. 



2. From the standpoint of cytology as well, the genus Crepis must 

 be considered as heterogeneous. Similarity of chromosome size seems 

 to be a better criterion of relationship than number alone, although 

 closely related species usually have the same numbers of chromosomes. 

 ]\Iost of the cytological heterogeneity is confined to the sections 

 Eucrepis ;m(l Catonia of Hoffmann's classification. The former is 

 found to be too heterogeneous both taxonomically and cj-tologically 

 to be retained as a section, and certain new subgroupings are needed 

 within it. Catonia also requires some drastic changes. It is hoped 

 that further study will reveal natural subgroups within Catonia; also 



