368 COMPOSITAE PETASITES 



78 Petasites Flowers white or purplish, the fertile ones pistillate and 

 more or less conspicuously radiate. 



* * Heads discoid, of wholly hermaphrodite fertile yellow flowers. 



79 Cacaliopsis Heads very many-flowered : anthers entire at base. 



80 Luina Heads about 10-flowered : anthers sagittate at base. 



81 Rainiera Heads 4-6-flowered : achenes prismatic. 



* * * Heads heretogamous or homogamous : the tubular disk flow- 

 ers perfect and fertile, with 2-cleft style. 



82 Crocidium Herbs with alternate leaves: heads radiate many-flower- 

 ed: flowers yellow, all fertile, involucre hemispherical or more open. 



83 Tetradymia Shrubs with alternate leaves : involucre of 4-6 firm and 

 concave close and overlapping bracts. 



84 Raillardella Herbs with alternate leaves : involucre of a single ser- 

 ies of linear equal bracts, their edges lightly connate below the middle : 

 pappus of comparatively few and usually stout plumose bristles. 



85 Arnica Herbs with chiefly opposite leaves: involucre of several thin, 

 herbaceous equal bracts : pappus a single series of numerous capillary 



"scabrous to barbellate bristles. 



86 Senecio Herbs with alternate leaves : involucre of several erect her- 

 baceous bracts: pappus of soft-capillary merely scabrous bristles. 



*Style-branches of hermaphrodite fertile flowers roundish-ob- 

 tuse, or at least not truncate, wholly without appendages or his- 

 pidity at summit. Receptacle naked, flat. Pappus-bristles merely 

 denticulate. 



78 PETASITES Gsertn. Fr. ii, 406, t. 166. 



Perennial herbs with thickish and mostly creeping rootstocks 

 sending up scapiform foliose bracteate simple flowering stems and 

 ample radical leaves on long petioles in early spring. Heads ra- 

 cemosely or corymbosely disposed, white or purplish-flowered, 

 subdioecious ; those of the truly fertile plant wholly or mostly of 

 pistillate flowers with slender tubular and irregularly 2-5-toothed 

 or distinctly^ ligulate corolla ; in the substerile with few of these 

 in the margin and numerous hermaphrodite infertile ones with 

 3-cleft or 3-lobed style and sterile ovary in the centre. Involucre 

 a series of soft herbaceoiis bracts. Achenes narrow, 5-10-costate. 

 Pappus of soft and white elongated bristles. 



P. sagittata Gray Bot,_ Cal. i, 407. Scapes very scaly, 3-10 inches 

 high ; leaves deltoid-ovate or reniform-ovate, persistently white-tomentose 

 beneath, glabrous or nearly so above, 4-10 inches long, their margins sin- 

 uate denticulate, neither cleft nor lobed : heads short-racemose, becoming 

 corymbose : involucre campanulate : flowers nearly white, the marginal 

 ones of the pistillate heads ligulate but not surpassing the disk. Wet 

 grounds, northern Washington to Alaska and across the Continent. 



P. palmata Gray I. c. Stems very scaly, stout, 6-34 inches high : 

 leaves nearly orbicular in outline, 6-18 inches in diameter, 7-11 cleft to 

 beyond the middle or deeper; the lobes o^long-Ianceolate to oblong-cune- 

 ate, laciniately dentate, white-tomentose beneath, green and glabrate 

 above: heads rather numerous, in a fastigiate panicle, about 6 lines high. 



