composiTtE. 63 



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

 large terminal areola bearing around the base of the st\'le a fleshy animlar disk. Lower 

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

 soft ones which thickly clothe the akenes. 



-1— -i— Akenes flattened, obcompressed, wing-margined. 



79. DICORIA. Female flowers one or two, wholly 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. Eeceptacle small, flat, with a few narrow and hyaline 

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

 delplious up to the lightly connected anthers ! the tube dilated and 5-tootlied at summit. 

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

 angled dorsally, abruptly bordered by a thiu-scarious pectinate-dentate wing or edge. Pap- 

 pus rudimentary, of several small and setiform squamella;. 



* * Heads unisexual, moncEcious ; 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 lieads in a raceme or spike of centripetal evolution : akenes turgid-ohovoid or ovoid, 

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

 Ainhrosiea', DC. 



-I— Involucre of the sterile heads gamopliyllous ; the receptacle low, and abortive style with 

 dilated apex radiately penicillatc or fimbriate. 



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

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

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

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

 silvory-scarious persistent transverse wings. , 



81. AMBROSIA. Involucre of the male flowers from depressed-hemisi)herical to turbinate, 

 .5-12-lol)ed or truncate, herbaceous. Receptacle flat or flatfish, usually with some filiform 

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

 acnminate. Involucre to the solitary fertile flower nucumentaceous, apiculate or beaked at 

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

 the lieak. Sterile lieads spicate or racemose above the fewer fertile ones. 



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

 the female. Fertile involucre 1-4-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 (the spiny free tips of component bracts) in more than one series. Leaves mostly 

 alternate. 



H— -i— 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 appendage mucronate : sterile style uuappendaged. Fertile heads a closed 

 and ovoid bur-like 2-celled and 2flowered involucre, 1-2-beaked at the ajicx, the surface 

 clothed witli uncinate-tipped prickles ■ each flower a single pistil, maturing a thick ovoid 

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



Subtribe 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 Heliopsis Icevis) : disk-flowers lierniapbrodite "and in our 

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

 draceous. Leaves opposite and lieads 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 awncd from the summit of the angles or edges. 



84. ZINNIA. Involucre cani])anulate or cylindraceous; its closely appressed-inibricated 

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



