Rvdberg : Rocky Mountain flora 161 



The species on which this genus is based was first described 



as a Prenantlies and later transferred to Lygodesmia. It is so 



unlike the other species of Lygodesmia 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 Nabalus {Prenantlies), but from this genus Pren- 



anthella is distinguished by the habit and the structure of the 

 involucre. 



J Prenanthella exigua (A. Gray) Rydb. 



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

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



New York Botanical Garden. 



