GExus 22. THISTLE FAMILY. 381 
Bog species ; inflorescence wand-like. 16. S. uliginosa. 
Upland species, the inflorescence various. 
Heads very short-peduncled. 
Leaves thick, firm in texture, little toothed or entire; tall species. 
Lower leaves ovate to broadly oval, serrate. 17. S. speciosa. 
Leaves lanceolate to oblong-lanceolate, entire. 18. S. rigidiuscula, 
Leaves thin in texture, at least the lower serrate; low species. 
Legs 19. S. Randii. 
Heads distinctly slender-peduncled. 
Basal leaves narrowly oblanceolate, 4” wide or less. 20. S. racemosa. 
Basal leaves broadly oblanceolate or obovate, 6”—-18” wide. 
Heads 4” high; basal leaves sharply serrate. 21. S. Gillmani. 
Heads 3” high; leaves nearly entire. 22. S. sciaphila, 
*** Heads in a terminal, usually large panicle, secund on its spreading or recurved branches. 
t Plant maritime ; leaves thick, fleshy, entire. 23. S. sempervirens. 
+i Plants not maritime ; leaves not fleshy. 
1. Leaves pinnately-veined, not triple-nerved. 
(a) Leaves all entire, thin and glabrous. 24. S. odora. 
(b) Leaves, at least the lower, more or less dentate or serrate. 
jt Leaves linear or linear-oblong, 1’-2’ long, scabrous. 25. S. tortifolia. 
tt Leaves broader, lanceolate, oblong, or ovate, 2’-10' long. 
¢ Stem densely pubescent; leaves more or less so. 
Leaves not rugose, sparingly dentate or entire. 26. S. fistulosa. 
Leaves rugose-veiny beneath, sharply serrate. 27. S. rugosa. 
43 Stem glabrous, or merely puberulent above. 
Leaves very rough on the upper surface, serrulate. 28. S. patutu. 
Leaves smooth, or minutely roughened on the upper surface. 
Racemes few, widely divergent, very slender. 
Lower leaves oblong, coarsely serrate, thin. 29. S.ulmifolia. 
Lower leaves ovate or lanceolate, rather finely serrate, firm. 30. S. Boottii. 
es numerous, spreading, recurved or ascending. 
Leaves all oblong or oblong-lanceolate, sessile. at.. S.. Eliott. 
At least the lower leaves petioled, lanceolate or ovate-lanceolate. 
Leaves firm, ovate-lanceolate or oblong-lanceolate; heads about 2” high; racemes short; 
Tays several. 32. S. neglecta. 
Leaves firm, narrowly lanceolate; heads about 2” high; racemes few, short; rays 1-5. 
33. S.uniligulata. 
Leaves firm, lanceolate or oval-lanceolate; heads 114”-21%4” high; racemes numerous, 
slender. 34. S. juncea. 
Leaves thin, the lower broadly ovate, short-acuminate; heads 21%4”-3%4” high; racemes 
numerous. 35. S. arguta. 
2. Leaves triple-nerved, i. e., with a pair of lateral veins much stronger than the others. 
Heads small, the involucre only 114” high or less; stem glabrous, or pubescent. 36. S. canadensis. 
Heads larger, the involucre 1144"-3” high. 
Stem glabrous. 
Leaves, and involucral bracts thin. 37. S. serotina. 
Leaves, and involucral bracts firm, somewhat rigid. 
Leaves linear-lanceolate ; achenes glabrous. 38. S. glaberrima. 
Leaves oblong-lanceolate; achenes silky-pubescent. 39. S. Shortii. 
Basal leaves oblanceolate, upper bract-like. 40. S. Ga tingeri. 
Stem pubescent or scabrous. 
Leaves lanceolate, sharply serrate or entire, rough above. 41. S. altissima. 
Leaves oblanceolate, spatulate, oblong, or ovate, the lower crenate. . 
Minutely rough-pubescent, grayish; lower leaves oblanceolate; heads 2”—3” high. 
42. S.nemoralis. 
Canescent and pale; leaves oblong or ovate; heads 3” high. 43. S. mollis. 
Very scabrous, green, not grayish, nor canescent. 44. S.radula, in 
Leaves broadly ovate-oval, sharply serrate, finely pubescent. 43. S. Drummondii. 
**%% Heads in a terminal, corymbiform, sometimes thyrsoid cyme, forming a flat-topped inflorescence. 
(Genus OL1conEvROoN Small.) 
Leaves ovate, oblong, or oval, mostly rough on both sides. 46. S.rigida. 
Leaves lanceolate, linear, oblong, or oblanceolate, glabrous or nearly so. ; 
Lower leaves oblong-lanceolate, serrulate. 47. S. ohioensis. 
Leaves all lanceolate or linear, entire. 
Stout; leaves lanceolate, the basal 812’ long. 48. S. Riddellii. 
Slender ; leaves linear, the basal 4’-5’ long. 49. S. Houghtoni. 
