246 COMPOSITE. Iva. 



* Heads nearly sessile, crowded in narrow spiciform clusters which are aggregated in a panicle. 



I. xanthiifolia, Nutt. Tall and coarse (3 to 5 feet high), pubescent, at least when young : 

 leaves mainly opposite, long-petioled, broadly ovate, ample, coarsely or incisely serrate, acu- 

 minate, 3-ril)bed at base, puberuleutly scabrous above, and when young canescent beneath : 

 panicles axillary and terminal : involucre depressed-hemispherical, biserial ; outer of 5 

 broadly ovate herbaceous bracts; inner of as many membranaceous dilated-obovate or trun- 

 cate ones, which are strongly concave at maturity and half embrace the obovate-])yriform 

 and glabrate akenes (on the apex of which sometimes persists a minute crown answering 

 to the obsolete corolla, or this wholly absent). — Gen. ii. 185. /. (Picrotus) xanthiifolia & 

 paniculata, Nutt. Trans. Am. Phil. Soc. vii. 347. Cyclacliccna xanthiifolia, Fresenius, 1. c. ; 

 Torr. & Gray, Fl. ii. 286. Euphrosi/ne xanthiifolia, Gray, PI. Wright, ii. 85. — Alluvial 

 ground or along streams. Saskatchewan and Nebraska to New Mexico, Utah, and Washing- 

 ton Terr. ; first coll. by Nnitall. 



I. dealbata, Gk vt. A foot or two high, canescent with floccose wool except the elongated 

 and narrow terminal panicle: leaves in greater part alternate, soft-tomentose, reticulate- 

 veiny (1^ to 3 inches long), from obscurely angulate-toothed to laciniately pinnatifid, cune- 

 ately or abruptly contracted at base into a short winged petiole : heads only a line long : 

 involucre of only 5 obovate concave somewhat herbaceous bracts: corolla of fertile flowers a 

 short cup or ring: akenes pyriform, roughish and glandular. — PI. Wright, i. 104. — Val- 

 leys of S. W. Texas, Wright, Bigelow. (Adj. Mex., Thurber, &c ) 



* -* Heads pedicellate, in looser panicles, more or less leafy- bracteate: habit and foliage of 

 Eiijjhrosync. 



I. ambrosisefolia. A foot or two high, hirsute or villous-hispid, paniculateh^ branched : 

 leaves almost all alternate, thin, twice or thrice pinnately parted into small oblong lobes: 

 involucre of 5 broadly ovate herbaceous outer bracts, and as many smaller obovate thin- 

 scarious inner ones: corolla of fertile flowers a mere vestige: akenes tur£iid-obovate. — 

 Euphrosiine amhrosicefolia. Gray, PI. Wright, i. 102, ii. 85. — W. borders of Texas and ad- 

 jacent New Mexico, Wright. (Mex.) 



§ 2. IvA proper. Heads spicately or rucemosely disposed in the axils of leaves 

 or foliaceous bracts, and nodding : fertile flowers with evident corolla. — Iva, 

 Torr. & Gray, Fl. ii. 28G ; Benth. & Hook. Gen. 1. c. 



* Heads in terminal and solitary or paniculate compact squarrosely bracteate spikes: leaves not 

 coriaceous: root annual. 



I. ciliata, Willd. Pather stout, 2 to 6 feet high, strigose-hispidulous and hispid : leaves 

 neai'ly all opposite, ovate, acuminate, sparsely serrate, the base abruptly contracted into a 

 hispid petiole : spikes strict, 3 to 8 inches long ; their bracts lanceolate and ovate-lanceolate, 

 foliaceous, surpassing the at length deflexed heads, hispid-ciliate, as are the 3 or 4 (rarely 5) 

 herbaceous and unequal distinct or partly united bracts of tlie involucre : akenes about 3, 

 obovate^ moderately flattish. — Spec. iii. 2386; Pur.sh, Fl. ii. 580; Torr. & Gray, Fl. ii. 287. 

 1. annua, Michx. Fl. ii. 184. not L., unless possibly the detailed illustration by Schmidel 

 should represent a state of it much altered in cultivation. Ambrosia Pilcheri, Torr. in 

 Hook. Conip. Bot. Mag. i. 99, with a var. having linear and much elongated bracts to the 

 spike. — Moist alluvial ground, Illinois to Nebraska, and south to Louisiana, Texas, and 

 New Mexico. (Adj. Mex., Berlandier.) 



* * Heads more loosely disposed in the axils of ordinary leaves, or upper ones commonly in the 

 axils of foliaceous bracts, 



-)— Rather many-flowered; the fertile flowers 5 or rarel}' fewer: perennials or shrubby, with thick- 



ish and (irm somewhat fleshy or coriaceous leaves. 

 ++ Bracts (if the fleshy-herbaceous involucre G to 9, imbricated in two or more ranks; and those 



among the numerous sterile flowers linear-spatulate. 

 I. imbricata, Walt. A foot or two high from a suffrutescent base, honey -scented, smooth 

 and glabrous or nearly so : stems thickish, ascending : leaves mainly alternate, fie.sh}', from 

 spatulate-oblong to narrowly lanceolate, sessile, sqme of the larger (1 or 2 inches long) 

 sparingly serrate : heads large for the genus (3 or 4 lines long), commonly jjcduuculate, the 

 lower surpassed by and the upper surpassing the subtending leaves : involucre hcmispherical- 

 campanulate, the outer bracts orbicular : sterile flowers many, the fertile 2 to 4 : akenes 



