368 COMPOSITE petabytes 



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

 more or less conspicuousely 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 Rainieria Heads 4-6-flowered : achenes prismatic. 



* * * Heads heterogamous or homogamous : the tubular disk. flowers 

 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 eqnal bracts, their edges lightly connate below the middle : 

 pappus of comparatively few and usually stout plumose bristles. 



85 Arnica Herhs with chiefly opposite leaves : involucre of several thin 

 herbaceous equal bracts: pappus a single series of numerous capillary 

 scabrous to barbellate bris;les. 



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-obtuse, 

 or at least not truncate, wholly without appendages or hispidity 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 scapiformfoliosebracteate simple flowering stems and 

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

 cemosely or corymbosely disposed, white or purplish-flowered, 

 subdioacious ; 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 

 2-cleft or 2-lobed style and sterile ovary in the centre. Involucre 

 a series of soft herbaceous 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 po 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 1. c. Stems very scaly, stout, 6-24 inches high: 

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

 beyond the middle or deeper; the lobes oblong-lanceolate to oblong-cune- 

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

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



