1929] ■ Babcock-Clausen : Meiosis in Crepis 419 



TAXONOMIC RELATIONS OF THE FIVE SPECIES 



According to a tentative taxonomic grouping (Babcock and Lesley, 

 1926, slightly modified) the five species discussed here would be classi- 

 fied as follows : 



SUBGENUS A. Achenes beaked 



Sec. III. Barkhausia 



Crepis hursifolia 

 Crepis taraxacifolia 



Sec. IV. Nemauchenes 



Crepis aspera 

 Crepis aculeata 



SUBGENUS B. Achenes not beaked 



Sec. VI. Eucrepis 



Crepis tectorum 



The above sections are distinguished primarily by the form of the 

 achenes. In Barkhausia, as tentatively used here, the achenes are 

 all similar and definitely beaked. In Nemauchenes they are of two 

 shapes, the marginal achenes being unbeaked and the inner ones 

 beaked. In Eucrepis the achenes are all unbeaked (or in a few species 

 very shortly beaked). The achenes of all but one of these five species 

 have been illustrated (Babcock and Lesley, 1926, fig. 3, g, h, h^ ; fig. 

 5, r). In Crepis aculeata the achenes resemble those of C. aspera but 

 are larger, while the marginal ones are less prominently angled and 

 the inner ones proportionately s4iorter beaked. 



Considering the meiotic behavior and fertility of the hybrids 

 herein discussed with reference to classification of the species involved, 

 it is clearly shown in tables 1 and 2 that the Crepis aspera X aculeata 

 hybrid displays the lowest amount of chromosome irregularities in 

 meiosis I with a large amount of regular pairing and very few pollen 

 mother cells showing detached chromosomes. The percentage of 

 irregularities in meiosis II is also low. In the C. taraxacifolia X 

 tectorum F^, on the other hand, less than one-third of the pollen 

 mother cells examined show regular pairing and a very large per- 

 centage have detached chromosomes. The C. aspera X hursifolia F^ 

 showed even less regularity in pairing in its pollen mother cells, but 

 the number of detached chromosomes observed was not so high as in 



