COMPOSITE. 63 



(sometimes with a single diaphanous and minute squamella to represent pappus!), with 

 large terminal areola bearing around the base of the style a fleshy annular disk. Lower 

 part of the disk-flowers and their chaff beset with some villous hairs, like tlie very long and 

 soft ones which thickly clothe the akenes. 



H— -i— Akenes flattened, obcompressed, wing-margined. 



79. DICORIA. Female flowers one or two, whoUy destitute of corolla ; male flowers 6 to 12, 

 with mere rudiments of ovary and style. Involucre of 5 oval or oblong herbaceous bracts ; 

 and within one or two larger and broad thin-scarious bracts, subtending the fertile flowers ; 

 or these wanting in male heads. Receptacle small, flat, with a few narrow and liyaline 

 chaffy bracts among the flowers. Filaments almost free from the obconical corolla, mona- 

 delphous up to the lightly connected anthers ! the tube dilated and 5-toothed at summit. 

 Akenes much surpassing the outer involucre, oblong, anteriorly flat, convex or somewhat 

 angled dorsally, abruptly bordered liy a thin-scarious pectinate-dentate wing or edge. Pap- 

 pus rudimentary, of several small and setlform squamellce. 



* * Heads unisexual, monoecious ; the fertile with solitary or 2 to 4 completely or nearly 

 apetalous female flowers in a closed nutlet-like or bur-like involucre, only the style- 

 branches ever exserted ; the sterile of numerous male flowers in an open involucre, 

 the heads in a raceme or spike of centripetal evolution ; akenes turgid-ohovoid or ovoid, 

 wholly destitute of pappus ; flowers greeiiisli or yellowish : male corollas obconical. — 

 Amhrosie<n, DC. 



•'I— Involucre of the sterile heads gamophyllous ; the receptacle low, and abortive style with 

 dilated apex radiately penicillate or fimbriate. 



80. HYMENOCLEA. Involucre of the male flowers saucer-shaped and 4-6-lobed, rarely 

 more cleft : bracts of the receptacle subtending the outer flowers obovate or spatulate ; inner 

 filiform or none : filaments distinct : anther-tips blunt. Involucre to the solitary fertile 

 flower ovoid or fusiform, beaked at apex, the lower part furnished with 9 to 12 dilated and 

 silvery-scarious persistent transverse wings. 



81. AMBROSIA. Involuci-e of the male flowers from depressed-hemispherical to turbinate, 

 .5-12-lobed or truncate, herl)aceous. Receptacle flat or flattish, usually witli some filiform 

 chaff among the outer flowers. Anther-tips (at first inflexed, at length erect) setiferous- 

 acuminate. Involucre to the solitary fertile flower uucumentaceous, apiculate or beaked at 

 the apex, and usually armed with 4 to 8 tubercles or short spines in a single series below 

 the beak. Sterile heads .spicate or racemose above the fewer fertile ones. • 



82. FRANSERIA. Heads of male flowers as Ambrosia, or sometimes intermixed with 

 the female. Fertile involucre l-J-flowered, 1-4-celled, a single pistil to each cell, 1-4- 

 rostrate, more or less bur-like, being armed over the surface with several or numerous prickles 

 or spines (tlie spiny free tips of component bracts) in more than one series. Leaves mostly 

 alternate. 



-1— -)— Involucre of the sterile heads polyphyllous, and the receptacle cylindraceous. 



83. XANTHIUM. Involucre of the globular sterile heads one or two series of small nar- 

 row bracts : receptacle distinctly paleaceous, a cuneate or linear-spatulate chaffy bract partly 

 enclosing each male flower ; filaments monadelphous : anthers distinct but connivent ; the 

 inflexed apical apjiendage mucronate : sterile style unappendaged. Fertile heads a closed 

 and ovoid l)ur-like 2-celIed and 2flowered involucre, 1-2-beaked at the apex, the surface 

 clothed with uncinate-tipped prickles • each flower a single pi.stil, maturing a thick ovoid 

 akene, the two permanently enclosed in the indurated pricldy involucre. Leaves alternate. 



Subtril;c IV. Zinnie./e. Ray-flowers ligulate and fertile ; the ligule with very short 

 tube or none, persistent on the akene and becoming papery in texture ! (but at length 

 falling or decaying away in Heliopds Icevu) : disk-flowers hermaphrodite and in our 

 genera fertile, numerous, subtended or embraced by chaffy bracts ; the corolla cylin- 

 draceous. Leaves opposite and heads singly terminating the stem or branches. 



* Leaves all or mostly entire: akenes of the disk compressed, all or some of them (either 

 of disk or ray) toothed or awned from the summit of the angles or edges. 



84. ZINNIA. Involucre campanulate or cylindraceous; its closely appressed-imbricated 

 bracts dry and firm, broad, with rounded summit often margined. Receptacle becoming 



