IVA COMPOSITE 335 



54 Centromadia Achenes of theray-flowers very oblique, the srr 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 Lagophylla Heads few-flowered : ray achenes about 5, obovate, much 



obcompressed, smooth : disk-flowers sterile : pappus none. 



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

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

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

 ulate pointed scales or none. 



57 Achyrachaena Heads many-lowered ; the flowers all fertile : achenes 



linear-cuneate or clavate, 10-ribbed, some or all of the ribs tuberculate- 

 scab ous ; those of the disk with a pappus of blunt, silvery-scarious 

 scales in 2 series. 



Subtribe i Ivese Heads androgynous, bearing few pistillate flowers 

 at the margin; the more numerous staminate ones all or most of them 

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

 rarely pointed. Involucre open. Achenes usually large for the size 

 of tne head, free. 



35 IVA L. Gen. n. 1059. 



Herbs or shrubs with entire or dentate or dissected leaves, at 

 least the lowest ones opposite, and small spicately or racemosely 

 or paniculately 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 3,), 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 rootstocks; 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 

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

 Saskatchewan. 



I. x ant hi folia 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 serrate, acuminate, 3-ribbed at base, 

 p'ubesoently 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 of as many mem- 



