508 Rydberg: Studies on the Rocky Mountain Flora 



grayish-tomentose beneath, deeply pinnatifid to about one fourth 

 from the midrib : lobes about 2 cm. long, lanceolate, few toothed or 

 lobed and tipped with moderately strong spines 4-10 mm. long : 

 heads hemispherical, 2.5-3 cm. high and 2.5-3.5 cm. broad: 

 outer bracts ovate, slightly floccose when young, entire, with a 

 narrow dorsal line, tipped with weak spines 1—2 mm. long, the 

 inner with dilated deltoid erose scarious acuminate tips : flowers 

 ochroleucous. 



A species closely related to the preceding, differing in the 



larger heads, longer spines, broader bracts and with erose instead 



of fimbriate tips. It grows in moist meadows at an altitude of 



about 2200 m. 



Colorado: Durango, 1896, Frank Tweedy \ 5/7 (type in U. 



S. Nat. Herb.). 



Garduus Americanus (A. Gray). 



a. 



Cirsium acule var. Americanus A. Gray, Proc. Acad. Phila. 

 1863 : 68. 



Cnicus Drummondii acaulesccns A. Gray, Proc. Am. Acad. 10 : 

 40, in part. 



Dr. Gray's Cirsium acanle var. Americanum is amply distinct 

 from C. Drummondii not only by the acaulescent habit, but also 

 by the narrower bracts and their long stout spines which are 1-2 

 cm. long while in C. Drummondii they are only a few mm. in 

 length and very weak. It is an alpine species growing at an alti- 

 tude of 2800-3500 m. To this belong the following specimens. 



Colorado : Silver Plume, 1895, p > A. Rydberg ; Como, South 

 Park, 1895, C. S. Crandall ; South Park, 1884, Letternian. 



v Carduus acaulescens (A. Gray) 



Cnicus Drummondii var. acaulesccns A. Gray, Proc. Am. Acad. 

 10 : 40, in part. 



Gray's variety acaulescens was based on two previously pub- 

 lished things, viz., Cirsium acaule var. Americanus A. Gray, given 

 above, and Cirsium Drummondii, " acaulescent form " D. C Eaton 

 in King's Report. As the first already has a valid name, I here 

 adopt the name acaulescens for the other part on which the variety 

 was founded. C. acaulescens resembles closely C. Americanus in 

 habit, but the spines of the outer and middle bracts are shorter and 



