RAGWEED FAMILY 829 



obconic. Filaments monadelphous. Corolla of the pistillate flowers wanting. 

 Achenes oblong, flat on the inside, convex or angled on the outside, with thin- 

 scarious, pectinately dentate wings. Pappus rudimentary, of a few small bristle- 

 hke scales. 



Upper leaf-blades broadly spatulate, ovate, or roundish. 



Inner liracts lO-l") mm. long; achene.s with pectinate margins. 1. D. WelherilUi. 



Inner bracts (l-s mm. long; achenes with contmuous erose margins. 2. D. canescens. 

 Leave.s all oblonfj-laneeolate to linear. 



Fertile Howers solitary in the heads; teeth of the achenes connected by a scarious 

 margin. 3. D. Brandegei. 



Fertile flowers 2 in each head; achenes without scarious margins. 4. D. paniculata. 



1. D. Wetherillii Eastw. Stems strigose; leaves spatulate, hirsute- 

 canescent with appressed hairs; staminate flowers several, longer than the outer 

 bracts; pistillate flowers usually 2; inner bracts hood-shaped, enclosing the 

 achenes, 10-15 mm. long, 10 mm. broad, intricately veined, pitted, glandular- 

 hairy; achenes oblong, mottled with brown, sparingly glandular. Sandy places: 

 s Utah. L. Son. 



2. D. canescens T. & G. Stem intricately branched, 3-10 dm. high, his- 

 pidulous; lower leaves opposite, lanceolate or oblong, coarsely toothed, the upper 

 alternate, round-ovate or orbicular, white with appressed pubescence, 1-3 cm. 

 long, crenate; fertile flowers 2; inner bracts petaloid, orbicular, concave; stam- 

 inate flowers many. Desert washes: se Calif. — Ariz. — s Utah. L. Son. 



3. D. Brandegei A. Gray. Stem diffusely branched, 3-10 dm. high, canes- 

 cent-hispid; leaves petioled; blades 1-5 cm. long, strigose-canescent, sinuate- 

 denticulate; heads few, some wholly staminate; fertile flowers sohtary; inner 

 bracts dilated-cuneate, rather small. Sandy bottoms: s Colo. — s Utah — Ariz. 

 Son. Au. 



4. D. paniculata Eastw. Stem 3-5 dm. high, branched from the base, his- 

 pid-canescent; leaf -blades sparingly dentate or entire, 1-2 cm. long; heads numer- 

 ous, paniculate; inner bracts large, truncate or obcordate, suborbicular, glandu- 

 lar-cihate; fertile flowers 2; achenes obovate, 6 mm. long, dark brown, dentate 

 with horny teeth; staminate flowers 9-10. Sandy flats: sw Colo. — se Utah. Son. 



5. HYMENOCLEA T. & G. 



Low shrubs. Heads unisexual, monoecious. Involucres of the staminate 

 heads saucer-shaped, of -4-6 more or less united bracts; paleae of the recei)tacle 

 subtending the outer flowers obovate or spatulate, those of the inner flowers fili- 

 form or none. Filaments distinct; anther-tips blunt; the abortive styles with 

 dilated fimbriate or penicillate tips. Involucres of the 1-flowered pistillate heads 

 ovoid or fusiform, beaked, with 9-12 dilated and silvery-scarious persistent 

 transverse wings on the lower portion. 



1. H. Salsola T. & G. Low shrubs, much branched, puberulent; leaves 

 alternate, linear-filiform, 1-5 cm. long; heads numerous, paniculate; staminate 

 heads hemispheric, 5 mm. broad, many-flowered; bracts of the pistillate invo- 

 lucre spirally arranged, imbricate, when dry spreading, suborbicular, 6-8 mm. 

 broad, silvery-scarious. Sahne soil: s Calif. — Nev. — s Utah — Ariz. L. Son. 



6. AMBROSIA (Tourn.) L. Ragweed, Roman Wormwood, 

 Bitter-weed. 



Annual or perennial, often more or less woodj^ caulescent herbs, mostly 

 monoecious, rarely dioecious. Leaves opposite or alternate, usually much 

 divided, or rarely merely toothed. Staminate heads in terminal spikes or 

 racemes. Involucres saucer-shaped or hemispheric, with 5-12 partly united 

 bracts; receptacle naked or with filiform jialeae. Corollas funnelform, 5-lobed. 

 Anthers mucronate at the apex; style rudimentary, brush-like at the apex. Pis- 

 tillate involucres enclosing tlie single flower, turbinate or subglobose, with several 

 tubercles or spines in a single series. Corolla wanting. Stigmas filiform. Achenes 

 ovoid or obovoid; pappus wanting. 



