The Origin of Crepis and Related Genera 13 



duced, the uppermost being bractlike. In certain very low or 

 tufted alpine species the flower heads may be few and on very 

 short scapes, or numerous and congested. The heads are large, 

 medium, or small and often many-flowered. The involucre is 

 generally composed of distinct outer and inner series of bracts. 

 The receptacle is naked or shortly ciliate (in two small sections 

 of Crepis it is paleaceous) . The corolla is tubular below, ligulate 

 above, and 5-dentate. The anther tube and style branches are 

 generally similar throughout except in color and such details as 

 the appendages, and the pappus consists of simple, barbellulate 

 brisdes. These are the outstanding resemblances between the 

 five genera. There are, however, numerous differences in the 

 vegetative parts, including the indumentum, also in details of 

 the inflorescence; and differences in the achenes and pappus, in 

 habit, and in color of the flowers are particularly useful for pur- 

 poses of classification. The differentiation in respect to some of 

 these features has been summarized from the diagnoses of Hoff- 

 man,^* Bentham and Hooker,^ Robinson and Fernald,'^ and 

 others, and is presented in very general, condensed form in 

 table I below. 



There are several small genera in the Crepidinae which re- 

 semble Crepis more or less, and no doubt they all deserve care- 

 ful consideration in any future revision of this subtribe. For 

 purposes of the present discussion, five have been selected which 

 have been merged previously with other genera and all of which, 

 the present writer believes, must be reinstated. It is not the pur- 

 pose of this discussion, however, to present the complete evi- 

 dence and formally to propose their reinstatement. They will be 

 used merely as illustrations of the usefulness of the cytological 

 criterion. Ixeris Cass, has been included in Lactuca by Hoff- 

 mann and it is certainly closer to Lactuca than to Crepis, but in 



