Genus 94-] 



THISTLE 



FAMILY. 



475 



I. Synosma suaveolens (L.) Raf. 

 Sweet-scented Indian Plantain. (Fig. 4032.) 



Cacalia suaveolens L. Sp. PI. S35. 1753. 



Senecio suaveolens EU. Bot. S. C. & Ga. 2:328. 1821-24. 



Synosma suaveolens Raf. ; Loud. Card. Mag. 8: 247. 1832. 



Glabrous or very nearly so throughout; stetu stri- 

 ate, o°-5° I'ig'i. leafy to the iuflorescence. Leaves 

 triangular lanceolate or hastate, sharply and irregu- 

 larly serrate, acuminate, 4'-io' long, 2'-6' wide at 

 the base, the auricles sometimes with i or 2 lobes 

 on the lower side; petioles margined, or those of 

 the basal leaves naked and slender; uppermost 

 leaves sometimes merelj- lanceolate and sessile; 

 heads 2"-3" broad in a usually large and compound 

 corymb; involucre 4"-6" high, its principal bracts 

 linear, acute; heads 20-30-flowered. 



In woods, Connecticut and New Jersey to Illinois 

 and Minnesota, south to Florida, West Virginia and 

 Kentucky, Called also Wild Caraway. Aug. -Oct. 



95. SENECIO L. Sp. PI. 866. 1753. 

 .\nnual or perennial herbs (some tropical species .shrubby or even arborescent), with 

 alternate or basal leaves, and solitary corymbose or paniculate many-flowered heads, of both 

 tubular and radiate, or only tubular flowers, in our species yellow. Involucre cylindric or 

 campanulate, its principal bracts in i series, distinct, or united at the base, usually with some 

 shorter outer ones. Receptacle flat or slightly convex, mostly naked, often honeycombed. 

 Rays, when present, pistillate, fertile. Disk-flowers perfect, fertile, their corollas tubular, 

 the limb 5-toothed or 5-lobed. .Anthers obtuse and entire at the base, or rarely slightly sag- 

 ittate. Style- branches of the disk-flowers usually recurving or spreading. .Achenes terete, 

 or those of the marginal flowers somewhat compressed, 5-10-ribbed, papillose or cauescent, 

 at least after wetting, and then usually emitting a pair of spiral threads. Pappus of numer- 

 ous slender or capillary, smooth or rough, mostly white bristles. [Latin, seiiex, an old man, 

 referring to the hoary character of sotne species, or to the white pappus.] 



.\n immense genus of probably at least looo species, of very wide geographic distribution. In 

 addition to the following, some 50 others occur in the southern and western parts of North America. 

 Our species known as Groundsel, Ragwort, or .Squaw-weed. 



-K- Heads conspicuously radiate (except in forms of Nos. 9, 10 and 15). 

 (a) Heads solitary or few, 6"-i2" high; northern species. 

 Stout; leaves 4'-8' long; heads i',i'-2' broad. i. S. Pseudo-Arnica. 



Low; leaves i'-2' long; heads Js'-i' broad. 2. S./rtgidus. 



(b) Heads several or numerous, cor>-mbose, mostly smaller. 

 t At least the lowest leaves entire or dentate, not pinnatifid (or sometimes pinnatifid in No. 7). 



X None of the leaves cordate. 

 Heads 5"-7" high; plants i°-s° tall; northwestern species. 

 Involucral bracts acuminate; leaves mostly entire. 



Bracts acute or obtuse, mostly black-tipped; leaves denticulate. 4. 



Heads 3"-5" high; plants 6' -30' tall. 



Leaves and stems persistently more or less tomentose or woolly. 

 Achenes glabrous. 

 Achenes hispidulous or glandular. 



Basal leaves long-petioled, crenate-dentate or sometimes pinnatifid; plants tall. 

 Basal leaves crenate-dentate; eastern. 6. S. lomenlosus. 



Stem leaves and often also the basal, pinnatifid; western. 7. .S*. Platlensis. 

 Basal leaves short-petioled, much tufted, oval, few-toothed, or entire; plant low. 



8. 5. antennariifolius. 

 Leaves glabrous or nearly so; stem often woolly, especially below. 

 Basal leaves obovate, spatulate, or oval : achenes glabrous. 



Basal leaves obovate or suborbicular, crenate or dentate; 



long. 

 Basalleavesovate to oval; involucral bracts 3"-5" long. 

 Basal leaves oblong; achenes hispidulous. 



S. inlegerrimus. 

 S. lumens. 



S. canus. 



involucral bracts 2" 

 9. i'. obovatus. 

 to. S. discoideus. 



-2%' 



Heads few or several, 3"-4" high; basal leaves i'-3' long. 

 2',i' high; basal leaves 3'-5' long. 



S. Balsamitae. 

 S. Smallii. 

 S. compactus. 



Heads numerous, 2"-2 ! 

 Basal leaves linear-cuneate, entire or 3-toothed at apex. 13. 



% X Basal leaves cordate or subcordate; plants mostly glabrous. 

 Basal leaves lanceolate or oblong-lanceolate. 14. S. Robbinsii. 



Basal leaves orbicular or ovate-oval. 15. 5. aureus. 



tt Leaves narrowly linear, entire, or with linear, entire lobes. 16. 5. Douglasii. 



ttt Leaves all pinnatifid or coarsely sinuate-dentate : plants glabrous, or somewhat woolly when young. 

 Leaves sinuate-dentate, lanceolate; heads 4"-5" high. 17. S. palustris. 



Leaves pinnately divided; segments entire or dentate; heads 2"-3" high. 18. S. lobalus. 

 Leaves 2-pinnatifid; heads 3" high; introduced species. 19. S. Jacobaea. 



-;■;- Heads discoid, the rays none, or minute. 



Leaves pinnatifid: plants glabrous or puberulent; achenes canescent. 

 Heads 3"-4" high; involucre naked, or nearly so at the base. 



20. S. sylvaticus. 



