ORDER 70. COMPOSITE. 161 



18. ASTER, L. In vol. oblong, imbricate. Scales loose, often with 

 green tips, the outer spreading. Disk fls. tubular, , ray fls. $ , in one row, 

 ligulate, 3-toothed at apex, finally revolute. Recep. flat, alveolate. Pap. 

 simple, capillary. Cypsela compressed. U Very abundant in the U. S., 

 flowering in late summer and autumn. Lvs. alternate, diminishing grad- 

 ually upward. Disk-flowers yellow, changing to purple ; ray-flowers blue-, 

 purple, or white, never yellow. Figs. 140, 388. (See also p. 446.) 



A Scales of the invo.ucre tipped with green or wholly green.. .( 1, 2, 3) 



B Scales destitute of green tips, white or scarious. Lvs. never cordate. . .( 4-p) 



1. BIOTIA. Heads corymbous, large. Rays 6 15, white. Lvs. cordate Nos. 1, 2 



2. CALLIASTRUM. Heads corymbous or few, large. Rays 1230, violet- 

 blue. Pap. bristles unequally thickened. Lvs. rigid, not cordate. . ..(a) 



a Lvs. ovate to lanceolate, serrate more or less. Fr. sinoothish Nos. 35 



a Leaves lance-linear to linear, b entire, merely acute Nos. 6, 7 



b bristly-fringed, pungent Nos. S, 9 



f 3. ASTERIA. Hds. panicled or racemed, rarely few. Pap. equal, soft. . .(c) 



c Leaves petiolate, the lower cordate, d evidently serrate Nos. 10, 11 



d entire or obscurely serrate. . .Nos. 1? -15 



c Leaves all sessile, entire, silky-canescent both sides. Pap. tawny .. ..Nos. 16, 17 

 c Lvs. not silky, d clasping with a cordate or auriculate base. . .(/) 

 d clasping with a broad base not cord, or auric. . .(/i) 

 d sessile with a narrow base, not clasping. . .(m) 



f Lvs. very small (!" 3"), entire. Scales with spreading tips Nos. 18, 19 



/ Leaves ordinary (I'fj^.e Scales with abrupt, appressed tips Nos. 20, 21 



e Scales loosely spreading. Lvs. entire Nos. 2225 



e Scales very loose. Lvs. long, serrate.,. . .Nos. 2(>, 27 



It Scales of the involucre closely imbricated (obtuse, No. 20), acute . . . .Nos. 2831 

 h Scales loose, or spreading, or recurved. k Pappus bright-colored. . .Nos. 32 34 



k Pappus tawny-brown Nos. 35, 36 



m Scales squarrous-spreading at the tips. o Hds. large (6"-10, purple. .Nos. 37, 33 



-o Hds. small (2-4"), whitish. .Nos. 45-47 



rn Scales loosely divergent, straight. Heads medium size, rays pale No. 43 



in. Scales erect, straight, in 1 row. Heads 23, or solitary, rays white No. 43 



rn Scales closely imbricated. n Hds. medium (3-"), purp. or pale. . .Nos. 43, 44, 31 



n Heads small (23"). white or pale Nos. 3941 



4. SCARIOSI. p Lvs. lanceolate, broadly or narrowly. Scales obtnsish Nos. 49 51 



p Lvs. subulate or lin. Scales very acute. s Hds. large, few . .Nos. 52, 53 



5 Hds. small, many. . .54 58 



1 A. corymbosus Ait. Nearly smooth ; Ivs. thin, ovate-acuminate, serrate, (he peti- 



oles wingless ; rays 6 9. Dry woods, N., M. 1 2f. Heads oblong, 4". Lvs. largo. 



2 A. macroplif llus Willd. Rough-pubescent ; leaves thickish, ovate, ecrrato witfc 



close teeth, petioles some winged ; rays 8-15. Woods, N. l-2f. Lvs. very large. Hds.G". 



3 A. mlrabilis T. & G. Lvs. ovate, serrate, the lowest petiolate, the ramial round 



ish ; invol. hemispherical, scales obtuse ; rays about 20. S. Car. Very rare. 



4 A. radula Ait. Lvs. lanceolate, acuminate, sessile, sharp-serrate, rough and rusjoua, 



invol. squarrous with the spreading scale-tips ; rays 20. N. 1 3f. 



5 A. gpcctabilis Ait. Lvs. lance-oblong, sessile, entire, the lower Etibserrate ; iuvol 



hemispherical, scales linear-spatulate, ciliate. Sands, Mass, to Fla. 1 2f. 



6 A. surculosus MX. Root a creeping, knotted rhizome ; Ivs. lance-linear and linear 



heads 15 ; scales linear-oblong, ciliate, inner obtuse. Wet. N. J. to Car. If. 

 . grdcilif. Heads 812, smaller ; rays 12 ; scales but slightly spreading. 



7 A. pal iidosus L. Slender, glabrous ; Ivs. long, linear ; hds. 1 6 ; scales lance-linenr 



rays 30, longer than the (6") invol. Swamps, S. 2 3f. Hends very large 



11 



