Rydberg : Rocky Mountain flora 467 



North Dakota, Montana, and northward far down the Mackenzie. 

 Dr. Greenman thought that the Colorado plant should be referred 

 to S. MacDougalii Heller, and so I adopted that view in the Flora 

 of Colorado. I have seen two specimens from Colorado which 

 may be included in 6". MacDougalii, but the rest belong to what I 

 think should be recognized as a distinct species. 



Senecio ambrosioides sp. nov. 

 Senecio eremophilus Porter & Coulter, Syn. Fl. Colo. 82, mainly. 



1874. Not S. eremophilus Richards. 

 Senecio MacDougalii Rydb. Fl. Colo. 397. 1906. Not S. Mac- 

 Dougalii Heller. 1899. 



Perennial, with a stout rootstock; stem glabrous, leafy, 4-10 

 dm. high ; leaves lanceolate or oblanceolate in outline, pinnatifid to 

 near the midrib or the lower incised, glabrous, all except the 

 uppermost short-petioled, the lobes lanceolate, coarsely dentate or 

 incised; heads numerous, corymbose-paniculate, 9-10 mm. high, 

 erect; involucres glabrous, 6 mm. high and about as broad; 

 bracts carinate, linear, acute, with black tips, the calyculate ones 

 subulate, 4-5 mm. long; ligules light yellow, 5-6 mm. long, 1.5-2 

 mm. wide; achenes minutely scabrous-puberulent on the angles. 



This species differs from Senecio MacDougalii in the larger 

 heads (in S. MacDougalii only about 7 mm. high), more campanu- 

 late involucres, lanceolate instead of linear divisions of the leaves, 

 and the achenes scabrous-puberulent on the angles. From S. 

 eremophilus it differs in the smaller and erect heads (in S. ere- 

 mophilus 10-12 mm. high), shorter rays, and smaller leaves. S. 

 ambrosioides grows in damp places at an altitude of 1800-3000 m. 

 Colorado: Green Mountain Falls, El Paso County, Aug. 2, 

 1892, C. S. Sheldon (type, in herb. N. Y. Bot. Gard.); above 

 Beaver Creek, July 8, 1896, Crandall jojo; Pagosa Peak, 1899, 

 Baker yo6; Parrott City, 1898, Baker, Earle & Tracy 475; Ute 

 Pass, 1896, Clements igo; Colorado Springs, July, 1893, Saunders; 

 Parlin, Aug. 16, 1901, B. H. Smith 127 ; Ruston Park, 1901, 

 Clements ij2; Mesa Yempa, 1898, Shear 3943; Chambers Lake, 

 1896, Baker; Ute Pass, 1896, Shear 36Q5; mountains between 

 Sunshine and Ward, 1902, Tweedy 4863; Empire, 1903, Tweedy 

 5783; Silver Plume, 1895, Shear 4QQ9; La Veta, 1896, Clements 

 166; Silver Plume, 1894, E. A. Bessey; Georgetown, 1878, 

 M. E. Jones 728; Gunnison, 1901, Baker 596. 



