Rydberg: Studies on Rocky Mountain Flora 185 



The group is closely related to the Aurei and Lobati with 

 which it is connected through 5. Plat tens is and#iS. Fendleri respec- 

 tively. S. Nelsonii and S. miiltilobus in young state may also be 

 sought here. 



Basal leaves mostly dentate or crenate. 



Basal leaves suborbicular, ovate or cordate ; margins of the petioles arachnoid- 



torn en tose. 



25. S. flaviilus. 



Basal leaves obovate or spatulate. 



Lower stem leaves acute ; plant dark green. 26. *S". Piatt en sis. 



Lower stem leaves obtuse ; plant yellowish-green. 27. S. Neo-Mexicanns 

 Basal leaves lanceolate or oblanceolate. 



Basal leaves narrowly oblanceolate, serrate. 28. .S". salicinus. 



Basal leaves lanceolate, sinuate-dentate. 29. S. canovirens. 



Some of the basal leaves entire or dentate, the rest pinnatifid or pinnately lobed. 

 Plant conspicuously rosulate-stoloniferous ; stem leaves sinuately round-lobed. 



30. S. rosulatus. 



Plant not stoloniferous ; stem leaves pinnatifid with toothed lobes. 



26. S. Plat/ens is. 



All leaves pinnatifid with toothed segments. 



Caudex subligneous ; plant torn en tose ; bracts shorter than the disk. 



31. S. Fendleri. 



Caudex not subligneous ; plant glabrate. 



Bracts almost equaling the disk. < 5. S. Nelsonii. 



Bracts much shorter than the disk. 4. S. maltilobus. 



25. Senecio flavulus Greene, Pittonia, 4: 108. 1900 



I have seen no specimens of this species, but from the descrip- 

 tion it must be most nearly related to the next, differing in the 

 more slender habit, the small leaves and their form and the peculiar 

 arachnoid tomentum on the margins of the petioles. The type 

 was collected by C. F. Baker at Aboles, Colo., in 1899. 



26. Senecio Plattensis Nutt. Trans. Am. Phil. Soc. II. 7: 4 I 3- 



1841 

 This species is exceedingly variable as to the leaf form as well 

 as to the pubescence ; usually the basal leaves are merely serrate 

 and obovate or oval in outline, but sometimes some of them are 

 like the lower stem leaves, more or less lyrately pinnatifid. It is 

 conspicuously floccose when young, but in age the leaves become 

 almost glabrous and the wool remaining only on the lower part 

 of the stem and petioles. The species belongs to the region of 

 the plains. [Plate 6, f. 14.] 



