248 SYSTEMATIC BOTANY. 



ing, somewhat shrubby, covered with white, silky down ; leaves bi- or in- 

 pinnately parted ; segments lanceolate, obtuse, often incised ; heads very 

 numerous, yellowish, nodding, racemose on the branches, forming a large, 

 leafy panicle. August. 



17. Gnaphalium. Heads many-flowered, discoid ; outer flower? 

 pistillate and slender; central ones perfect. Involucre-scales imbri- 

 cated, scarious, white or colored. Receptacle flat, naked. Pappus 

 simple, rough, capillary. 



1. G. POLYCEPHALUM (Life Everlasting). Stem erect, branching, 

 covered with cottony down ; leaves linear-lanceolate, tapering at base, ses- 

 sile, white downy beneath, nearly smooth above ; heads in dense clusters at 

 the summit of the branches, corymbose, fragrant ; involucre-scales ovate, 

 acute, whitish ; flowers yellowish. In fields, 1-2 feet high. August-Sep- 

 tember. 



2. G. ULIGINOSUM (Cudweed}. Woolly ; stem low, diffusely branched ; 

 leaves lanceolate or linear ; heads small, in sessile, terminal, crowded, leafy 

 clusters ; involucre-scales oblong, yellowish. In low grounds, 3'-6' high. 

 A ugust-September. 



18. Antennaria. Heads many-flowered, dioecious ; pistillate heads 

 with filiform corollas. Involucre-scales imbricated, scarious, white or 

 colored. Receptacle not chaffy. Pappus simple, bristly. y. 



1. A. MARGARITACEA (Pearl Everlasting). Stem erect, leafy, white- 

 downy, corymbose above ; leaves linear-lanceolate, sessile ; heads in a ter- 

 minal, flat corymb ; involucre-scales elliptic, obtuse, pearly white ; flowers 

 yellowish. In fields and pastures, 1-2 feet high. August. 



2. A. PLANTAGINIFOLIA (Mouse-ear Everlasting). Stoloniferous ; stem 

 simple, downy ; leaves white and silky when young, at length green above 

 and hoary beneath ; heads small, aggregate in a dense, terminal corymb ; 

 involucre-scales mostly white ; outer ones more or less obtuse. In old fields 

 and pastures, 3'-6' high. April-July. 



19. Xanthium. Sterile and fertile flowers in different heads upon 

 the same plant. Sterile involucre imbricated ; receptacle chaffy. Fer- 

 tile involucre closed, 2-leaved, covered with hooked prickles, 2-flow- 

 ered. 



X. STRUMARIUM (Clot-weed). Stem erect, unarmed, branching; leaves 

 cordate, 3~5-lobed, dentate, rough ; fruit oval, with 2 straight beaks. Stem 

 2-4 feet high. August-September. 



20. Ambrosia. Sterile and fertile flowers in different heads upon 

 the same plant. Sterile involucre hemispherical. Staminate flowers 

 5 or more, funnel-form. Fertile involucre i-leaved, closed, i-flow- 

 ered. 



i. A. TRIFIDA (Great Rag-weed}. Hairy, rough; stem tall, square, 

 stout, usually branching ; leaves large, opposite, usually 3-lobed, serrate ; 



