IVA 



COMPOSITE 335 



54 Centromadia Achenes of theray-flowers very oblique, the str all ter- 



minal areola from the summit of the inner angle or face, on a narrow 

 beak : receptacle convex or couical, chaffy throughout, the chaff distinct. 



* * * Bay-achenes obcompressed or clavate. completely enclosed 

 in the involucral bracts which are flattish on the back at base and their 

 thin margins abruptly infolded. 



55 LasropliTlla Heads few-flowered: ray achenes about 5, obovate, much 



obcorn pressed, smooth: disk-flowers sterile : pappus none. 



56 Layia Heads many-flowered: rays 8-20, with obovate or somewhat 

 clavate smooth aehi-Mes; disk-flowers mostly fertile, their similar or 

 narrower achenes often pubescent : pappus composed of bristles or sub- 

 ulate pointed scales or none. 



57 Acliyraehsena Heads many-J9owered ; the flowers all fertile: achenes 



linear-cuneate or clavate. ld-ribbed, some or all of the ribs tuberculate- 

 scab ous: those of the disk with a pappus of blunt, silvery-searious 

 scales in 2 series. 



Subtribe i Ivea Heads androgynous, I w pistiU 



at the margin; the more numerous staminaU - 11 or most of them 

 subtended by slender chaffy bracts. Anther-tips short and obtuse : 

 ed. Involucre open. Achenes usually I 



of tne head. free. 



35 IVA L. Gen. n. 1059. 



Herbs or shrubs with entire or dentate or dissected leave-, at 

 least the lowest ones opposite, and small spicately or racemosely 

 or panieulately disposed or scattered and commonly nodding heads 

 of inconspicuous flowers. Fertile and sterile flowers in the same 

 heads: the former 1—5. marginal, with a small tubular corolla; the 

 latter 7-20 (rarely only 2 or o), with tubular-campanulate or fun- 

 nelform 5-toothed corolla. Bracts of the campanulate or hemi- 

 spherical involucre 3-5, in a single series and more or less united 

 into a cup. Receptacle chaffy with linear or spatulate scales sub- 

 tending the sterile flowers. Anthers nearly distinct. Style in 

 the fertile flowers deeply 2-cleft: of the sterile ones undivided. 

 Achenes obovate, thick, often granulate without a disk at the 

 apex. Pappus wanting. 



I. axillaris Pursh Fl. 743- Herbaceous from somewhat woody creep- 

 ing rooratocks; the stems or branches nearly simple, ascending, 10-20 



inches high : leaves obovate or oblong to nearly linear, obtuse, entire, ses- 

 sile, rarely over an inch long, even the uppermost usually much surpassing 

 the mostly solitary heads in their axiles: bracts of the hemispherical 

 involucre connate into a 4-5-lobed or sometimes parted and sometimes 

 merely crenate cup : bracts of the receptacle reduced to filiform chaff. In 

 saline or sandy places. Brit. Columbia to California New Mex. and the 

 Saskatchewan. 



I. xanthifolia Nutt. Gen. ii. 185 <; Tall and coarse { 3-5 feet high), pu- 

 bescent, at least when young: leaves mainly opposite, long-petioled, broad- 

 ly ovate, ample coarsely or incisely sernite, acuminate, 3-ribbed at base, 

 pubescently scabrous above and when young canescent beneath : heads 

 nearly sessile, crowded in narrow spiciform clusters which are aggregated 

 in axillary and terminal panicles: involucre depressed-hemispheric, biser- 

 ial, the outer of 5 broadly ovate herbaceous bracts; inner ot as many mem- 



