Rydberg : Rocky Mountain flora 161 



The species on which this genus is based was first described 

 as a Prcnauthcs and later transferred to Lygodesviia. It is so 

 unUke the other species of Lygodcsiiiia in habit, that the habit 

 alone would suggest a distinct genus. But the best character is 

 found in the achenes, which are ribbed and tapering downward from 

 the summit instead of upwards from the base. The fruit agrees 

 better with that of Nahalns {Prcnauthcs), but from this genus Pi-cn- 

 antJiclla is distinguished by the habit and the structure of the 

 involucre. 



Prenanthella exigua (A. Gray) Rydb. 

 ProiaiitJics exigua A. Gray, PI. Wright. 2 : 105. 1853. 

 Lygodesmia exigua A. Gray, Proc. Am. Acad. 9 : 217. 1874. 

 New York Botanical Garden. 



