No. 632] SHORTER ARTICLES AND DISCUSSION 273 



sible of those features most favorable to securing the desired 

 results. 



With this explanatory introduction let us consider briefly the 

 present state of our knowledge of Crepis with reference espe- 

 cially to its promise of usefulness in genetic studies. 1 This genus 

 belonging to the chicory tribe of the Composite contains about 

 200 species (according to Index Kewensis) which are widely 

 scattered, the genus being represented by indigenous species in 

 every continent and in Australasia. Just how great is the diver- 

 sity in morphological characters within the genus remains to be 

 seen, but the wide distribution of the group as a whole and of 

 some of the individual species would lead one to expect a large 

 number of diverse characters and many different combinations 

 of the same. The descriptive connotation of many of the specific 

 names also indicates a remarkable diversity among these forms. 

 For example, there are giants and pigmies, there are forms with 

 bristly, woolly, floury, and glandular pubescence as well as 

 glabrous forms, there are four or more flower colors and one 

 species is named "bicolor." This expectation has been borne out 

 by such observations on preserved and living specimens as the 

 writer has been able to make. There are annual, biennial and 

 perennial species which should prove to be very interesting 

 forms for interspecific hybridization studies. Finally, within 

 at least two of the individual species, there certainly exists a 

 remarkable diversity of forms. 



But it is not for its wealth of variation alone that this genus 

 is especially interesting to geneticists. The cytological investi- 

 gations which have been made on a dozen or more species of 

 Crepis reveal a most interesting situation as regards chromosome 

 numbers. There is at least one species (possibly two or three) 

 having only 3 for the haploid number of chromosomes, a group 

 of six or seven species with 4 chromosomes, another group of 

 four species with 5, a single species with 8, another with 9, and 

 still another with 20 chromosomes as the reduced number. The 

 absence of a common denominator greater than one for this series 

 of numbers has caused some interesting speculations as to the 

 method of derivation of one species from another (Rosenberg, 

 1918). Several cytologists have also noted the fact that the chro- 



