160 Rydbkrg : Rocky Mountain flora 



tapering below into petioles about 3 cm. long ; inflorescence corym- 

 biform ; heads about 4, about 12 mm. high; involucres obconic- 

 turbinate, floccose at the base ; bracts linear, gradually acute ; rays 

 pale-yellow, 8-9 mm. long, 3 mm. wide. 



This species is probably most closely related to 5. pentodontus, 

 but distinguished by the peculiar involucre, which tapers gradually 

 into the peduncles. 



Colorado: Lake City, 1878, H. N. Pease. 





Senecio multicapitatus Greenman, sp. nov. 



Perennial with a thick woody root ; stem 4-10 dm. high, yel- 

 lowish, glabrous, branched and broom-like, leafy ; leaves irregu- 

 larly pinnately dissected into linear-filiform lobes, 1 — 1 . 5 mm. wide, 

 or the upper simple and linear-filiform, somewhat fleshy, glabrous 

 and yellowish-green ; heads in a corymbiform inflorescence, nu- 

 merous, almost cylindric, 7-8 mm. high, about 4 mm. in diam- 

 eter ; bracts 8-10, yellowish, linear, gradually acute, glabrous and 

 shining ; calyculate ones small, subulate ; rays pale-yellow, 7-8 

 mm. long and 2 mm. wide ; achenes striate, grayish strigose- 

 hispidulous. 



This species has been included in 5. Doug/asii, which has long 

 calyculate bracts and is confined to the west coast. S. multicap- 

 itatus resembles closely 5. Riddellii in habit, but differs in the 

 narrow heads and few bracts. In S. Riddellii the bracts are 12-1 5 

 and the involucre campanulate. S. multicapitatus grows on plains 

 and in mountain valleys of Colorado, New Mexico, and Arizona. 



Colorado : Huerfano Valley, near Gardner, 1900, F. R. Vree- 

 land6§i; Mt. Princeton Station, 1901, Undcrzvood & Selby 46 j. 



New Mexico: Gray, Lincoln Co., F. S. Earle & Ester S. 

 Earle ; high plains north of El Capitan Mountains, F. S. Earle & 

 Ester S. Earle 388. 



Arizona : Holbrook, 1896, Myrtle Zuck. 



PRENANTHELLA Rydb. gen. nov. 



Low diffusely branched annuals, with numerous small heads 

 terminating the branches. Lower leaves ample, oblong or spatulate 

 in outline, more or less runcinate ; the upper reduced and bract-like. 

 Involucres oblong, 4-5 -flowered with as many oblong bracts and 

 1 or 2 small calyculate ones. Achenes gradually tapering down- 

 ward from the truncate summit, 4-5-ridged. Pappus of white soft 

 capillary bristles. 



