336 COMPOSITiE ambeobia 



' O^BTNBBIA 



branaceous dilated-obovate or truncate ones which, are strongly concave 

 at maturity and half embrace the obovate-pyriform iand glabrate akenes." 

 Idaho and eastward. 



Subtribe ii, Ambrosiem DO. Prodr. v, 522. Head$< unisexual, 

 moncecious; the fertile with solitary or 2—4 completely apetalous or 

 nearly apetalous pistillate flowers in a closed nut-like or bur-like-ivo- 

 lucre, only the style-branehes ever exserted : the sterile of numerous 

 staminate greenish or yellowish flowers with obconical corollas in an 

 open involucre, the heads in a raceme or spike of centripetal evolu' 

 tion. Achenes turqid-obovoid or ovoid. Pappus wholly wanting. 



* Involncral bracts of the staminate head united. Receptaccle low. 



36 AMBROSIA Tourn. L. Gen. n. 1057. 



Coarse branching monojcious or rarely dioecious herbs with 

 mostly lobed or dissected opposite and alternate leaves and small 

 heads of greenish flowers, the staminate heads racemose or spicate, 

 without subtending bracts; the pistillate below, commonly in 

 small clusters in the axils of leaves or bracts. Involucre of the 

 pistillate heads globoge-ovoid or top-shaped, closed, 1-flowered, 

 nsually armed with 4-8 tubercles or spines : corolla none. Stamens 

 none, style-branches filiform: of the staminate heads mostly 

 hemispheric or saucer-shaped, 5-12-lobed, opeu, many-flowered. 

 Receptacle nearly flat, naked, or with filiform chafi'. Corolla 

 funnelform, 5-toothed. Style undivided, pencillate at the apex. 



A. artemigisBfolia L. Sp. 987. Pubescent, puberulent or hirsnte pan- 

 iculately braached annual, 1-6 feet hieh : leaves thin, bipinnatifld or pin- 

 nately parted with the divisions irregularly pinnatifid.or sometimes nearly 

 entire, on the flowering branches often undivided : racemes of sterile heads 

 very numerous, 1-6 inches long, the involucres hemispheric, crenate, the 

 receptacle chaSy : fertile heads obovoid or subglobose, mostly clustered, 

 1-2 lines long, short-beaked, 4-6-spined near the summit, sparingly pubes- 

 cent. Dry plains and fields, eastern Washington 'to Brit. Columbia and 

 the eastern States. 



37 G^RTNERIA Medicus Act.' Pal. iii, 244. 

 FRANSERIA Cav. 



Herbs or woody plants with chiefly alternate, lobed or divided 

 leaves and small monoecious rayless heads of greenish flowers: the 

 staminate numerous, in terminal spikes or racemes: the pistillate 

 solitary or clustered in the axils of the upper leaves. Involucre 

 of the pistillate heads ovoid or globose, closed, 1-4-celled, 1-4- 

 beaked, armed with several rows of spines and forming a bur in 

 fruit: corolla none or rudimentary; style deeply bifid, its branch- 

 es exserted; stamens none; achenes obovoid, thick, solitary in the 

 cells: pappus none. Staminate heads sessile or short-peduncled, 

 their involucres broadly hemispheric, open, 5-12-lobed; recepta- 

 cle chaffy: corolla regular, the tube short, the limb 5— lobed: style 

 undivided : anthers scarcely coherent, mucronate tipped. 



G. acanthocarpa Brit. Mem. Torr. Club v, .S32. Frameria Hookeriana 



