1915] 



GREENMAN MONOGRAPH OF SENECIO 579 



Key to the Species 



A. Heads radiate or discoid; rays when present minute, 



barely surpassing the involucre. 



a. Plants viscid-pubescent 1. S. visoosus 



b. Plants glabrous or pubescent, not viscid. 



a. Leaves coarsely dentate, auriculate-clasping by 



a broad base 2. 8. mohavensis 



/3. Leaves chiefly pinnatifid, not greatly expanded 



at the base. 



I. Bracteoles black-tipped, heads discoid 3. 8. vulgaris 



II. Bracteoles not black- tipped; heads minutely 



radiate. 



1. Plants slightly pubescent //. 8. sylvaticus 



2. Plants glabrous 5. 8. aphanactis 



B. Heads radiate; rays conspicuous, much surpassing the 



involucre. 



a. Plants glabrous or pubescent, not arachnoid- 



tomentose. 



a. Leaves thin 6. 8. calif ornicus 



p. Leaves thickish, succulent 6a. var. ammophilus 



b. Plants arachnoid- tomentose 7. 8. ampullaceus 



1. Senecio viscosus L. Sp. PL 2 : 868. 1753, and ed. 2, 1217. 

 1763 ; Sow. Eng. Bot. pi. 32. 1790 ; Willd. Sp. PI. 3 : 1984. 1800 

 Oeder, Fl. Dan. pi. 1230. 1799 ; Schkuhr, Handb. pi. 267. 1808 

 DC. Prodr. 6 : 342. 1837 ; Gray, Syn. Fl. N. Am. I 2 : 394. 1884 

 Greenm. Monogr. Senecio, I. Toil, 23. 1901, in Engl. Bot 

 Jahrb. 32 : 19. 1902, and in Gray, Manual, ed. 7, 853. 1907 



Britton, Manual, ed. 2, 1029. 1905; Britton & Brown, 111. 

 FL, ed. 2, 3 : 540. 1913. 



Obaejaca viscosa Cass. Diet. Sci. Nat. 35 : 270. 1825. 



A strong-scented annual, viscid-pubescent throughout ; stem 

 erect, 2 to 4 dm. high, usually branched from the base ; leaves 

 sessile, half-clasping, 3 to 6 cm. long, two-thirds as broad, 



once or twice pinnatifid with angulate-sinuate lobes and 



rounded sinuses; heads radiate (rarely discoid); rays incon- 

 spicuous; achenes glabrous. 



Distribution: eastern North America from Nova Scotia 

 to Pennsylvania, near the coast. 



Specimens examined : 



Nova Scotia: Pictou, 1 Nov., 1874, Fowler (Field Mus. 



Herb.); Pictou Landing, 21 July, 1883, Macoun 14883 (Geo! 



Surv. Canada Herb.) ; Kentville, 22 Aug., 1902, Fernald (Gray 

 Herb, and Geol. Surv. Canada Herb.). 



New Brunswick: Schediac, 11 Sept., 1874, Fowler (Geol. 



