The Origin of Crepis and Related Genera 15 



the strict sense of Cassini's definition' it cannot belong in Lac- 

 tuca, because the achenes are not strongly compressed and they 

 are lo-ribbed, the ribs being equal and often salient or rounded. 

 Hence the present author agrees with Gray" and Nakai^ in their 

 reinstatement of this genus. The genus Youngia Cass, is included 

 in Crepis by Hoffmann, and it resembles Crepis more than it 

 does Lactuca; but unfortunately Youngia has been made a re- 

 pository for a number of species which cannot be classified here 

 in the sense of Cassini's definition.* Because of the strongly ob- 

 compressed marginal achenes and certain other details, Youngia 

 Cass., sensu stricto, must also stand as a genus intermediate be- 

 tween Crepis and Lactuca. The genus Aetheorrhiza Cass, is 

 monotypic and the species has long been known as Crepis 

 bulbosa (L.) Tausch. Because of the imbricate involucre and the 

 peculiar achenes, which are superficially like those of Crepis but 

 are actually unique, this genus should be reinstated. Another 

 species to be excluded from Crepis is Paleya oligocephala Sch. 

 Bip. The multiseriate, imbricate involucre is alone sufficient to 

 bar it from Crepis, Lactuca, Hieracium, and Prenanthes. As the 

 type species of this genus was Crepis albida VilL, the genus has 

 become synonymous with Crepis. The only other species that 

 has been published under Paleya (P. billotioides Sch. Bip.) is 

 also received under Crepis. Hence P. oligocephala may constitute 

 a monotypic genus. However, its relationships to certain other 

 dubious species await investigation. 



In addition to the foregoing, two small genera have been 

 erected by Nakai^ for the disposition of certain species which he 

 considers neither Crepis nor Lactuca. They both resemble Ixeris 

 in some degree, but one of them, Crepidiastrum, is strongly 

 suflrutescent or shrublike and differs in habit, leaf arrange- 

 ment, and especially in the Crepis-likc achenes, which are terete 



