246 COMPOSITiE. Iva. 



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

 ' I. xanthiifolia, Nitt. 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-ribbed at base, puberulently scabrous above, and when young canescent beneath : 

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

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

 cate ones, whicli are strongly concave at maturity and half embrace the obovate-pyriform 

 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. /. [Picrotiis] xanthiifolia & 

 panicidata, Nutt. Trans. Am. Phil. Soc. vii. 347. Cijcliichima 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 Idaho; 

 first coll. by Nuttall. 

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

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

 veiny (1| to 3 inches long), from obscurely angulate-toothed to laciuiately piuuatifld, 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. — Y al- 

 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 

 Euphrosi/ne. 



I. ambrosisefolia. A foot or two high, hirsute or villous-hispid, paniculately 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 turgid-obovate. — 

 Euphrosi/ne ambrosicefolia, Gray, PI. Wright, i. 102, ii. 85. — W. borders of Texas and ad- 

 jacent New Mexico, Wright. (Mex.) 



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

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

 Terr. & Gray, Fl. ii. 286 ; Benth. & Hook. Gen. 1. c. 



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

 coriaceous : root annual. 



'I. ciliata, Willd. Rather stout, 2 to 6 feet high, strigose-hispidnlous and hispid: leaves 

 nearly 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 deflexcil heads, hispid-ciliate, as are the 3 ur -1 (rarely 5) 

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

 obovate, moderately flattish. — Spec. iii. 2386; Pursh, Fl. ii. 580; Torr. & Gray, Fl. ii. 2S7. 

 I. annua, Michx. Fl. ii. 184, not L, rmless possibly the detailed illustration by Schmidel 

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

 Hook. Comp. Pot. JIag. 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 ilexico. (Adj. Mex., Berlanclier.) 



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

 axils of foliaceous bracts, 



-K- liather many-flowered; the fertile flowers 5 or rarely fewer: perennials or shrubby, withthick- 



ish and firm somewhat fleshy ur coriaceous leaves. 

 ++ Bracts of the fleshy-herbaceous involucre 6 to 9, imbricated in two or more ranks; and those 



among the numerous sterile flowers linear-spatulate. 

 I. imbricata, \Valt. A foot or two high from a suffintcscont base, honey-scented, smooth 

 and glabrous or nearly so: stems thickish, ascending: lea\es mainly ;xlternate, fleshy, from 

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

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

 lower surpassed by and the upjicr sur])assing the .stibtcnding leaves : involucre hcmispherical- 

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



