240 COMPOSITE. Acantliospermum. 



A. iiiJmile, DC. Larger, commonly erect, hirsute: leiives wing-petioled or sessile by a 

 cuneate base : fructiferous bracts somewhat S-angletl, not grooved, armed (besides the 

 prickles) wieh one or two long spines from the truncate summit. — A. liumilc & A. Iiisjiidum, 

 DC. 1. c. Melampodium hnmile, Swartz, Prodr. 114. Ccntrospermurti hiimi/e, Less. Syn. 

 217. — Ballast-weed, about Philadelphia and New York; naturalized at Peusacola. (Nat. 

 from W. Ind.) 



70. SILPHIUM, L. Rosin-weed. (St'A^tov, ancient name of an Um- 

 belliferous plant in N. Africa which produced a gum-resin, transferred by Lin- 

 nanis, in his accustomed way, to an American genus.) — Tall and coarse perennials 

 (all of Atlantic U. S.) ; with resinous juice, thick roots, commonly large leaves, 

 and ample pedunculate heads- of yellow flowers (one species with white rays !), 

 produced in summer and autumn. — Torr. & Gray, Fl. ii. 275 ; Benth. & Hook. 

 Gen. ii. 350. 



* Stem square, leafy to the top : bases of the leaves or of their winged petioles cupulate-comiate. 

 S. perf oliatum, L. (Cup-plant.) Stem 4 to 8 feet high, commonly very smooth and 

 gl.abrous : leaves either smooth or scabrous, sometimes hirsute-pubescent l)eneath, ovate or 

 the upper ovate-lanceolate (the larger a foot or more long), dentate or denticulate with 

 mucronate teeth; upper ones united by their broad bases and lower by winged petioles 

 into a perfoliate cup : heads terminating the loosely cymosely disposed flowering branches, 

 on naked peduncles : involucre short-campanulate, half or two-thirds inch high ; outer bracts 

 ovate, from erect to somewhat squarrose-spreading : rays inch long : akeues either witli deep 

 or sliallow notch, jjhe narrow wings being produced either into very small obsolete or prom- 

 inent triangular teeth. — Spec. ed. 2, ii. 1.301 ; Gouan, Hort. Monsp. 462; Hook. Bot. IMag. 

 t. .3.354 ; Torr. & Gray, 1. c. S. connutum, L. Mant. 574, a form with branches somewhat 

 hispid. S. tetragonum & S. scahrum, Moench, Meth. 606. S. conjunctutn, Willd. Enum. 

 633. S. Hornemanni, Schrad. Hort. Ga>tt. ; DC. Prodr. v. 514. S. eri/throatulon, Bernh. in 

 Spreng. Syst. iii. 630. — Alluvial soil, Michigan and Wisconsin to Upper Georgia and 

 Louisiana. Common in cultivation; variable but characteristic. 



=;■,: * Stem from obtusely quadrangular to terete, leafy : leaves all or some of tliem opposite, entire 



or serrate, not connate-perfoliate, 

 •I— All but the lower sessile, and either all opposite or the upper pairs occasionally disjoined: 



akenes Avith a broad wing and a deep narrow notch: stems 2 to 4 feet high, rigid, very leafy 



to the top. 

 S. integrifolium, Michx. Stem smooth or scabrous, sometimes rough-hi.spidnlous : leaves 

 entire or denticulate, lanceolate-ovate or ovate-lanceolate ; all tiie upper ones closely sessile 

 by a broad and roundish or subcordate partly clasping base, and tapering from below tlie 

 middle to an acute apex, scabrous above, from nearly glabrous and smooth to cinereous- 

 pubescent beneath, 3 to 5 inches long, commonly of firm texture : heads somewhat corym- 

 bo.se, nearly all short-pcduncled : involucre over half-inch high ; its bracts mostly ovate and 

 spreading : akenes broadly obovate, the body 4 lines long, the scarious wing a line or so wide, at 

 least toward the summit. — Fl. ii. 146 ; Torr. & Gray, Tl. ii. 279, hardly of Ell. 5^. !(rvi- 

 gatitm, Pursli, as to char. 6\ speciosnm, Nutt. Trans. Am. Phil. Soc. vii. 341, a very smooth 

 form, the var. Ui've, Torr. & Gray, 1. c. — Prairies, &c., Wisconsin and Illinois to Arkansas 

 and Texas, and possibly to W. Georgia. 

 S. asperrimum, Hook. Commonly taller: stem rough-hispid: leaver of the jireceding 

 but more scabrous : heads generally larger : akenes with broader wings, the triangular 

 a])ical portions 2 or 3 lines high. — Comp. Bot. Mag. i. 99. S. radula, Nutt. Trans. Am.' 

 Phil. Soc. 1. c. S. scaberrimum, Torr. & Gray, Fl. ii. 279, var. y, hardly Ell. — Plains of 

 Arkansas, Louisiana, and Texas. 

 S. scaberrimum, Ell. Stem and commonly both sides of the leaves hispid : leaves in 

 remoter ])airs, thinner, oblong or ovate, all but the uppermost rather coarsely serrate and 

 with narrowed or even short petiole-like base (the larger 4 to 6 inclies long) : heads fewer, 

 more pedunculate: rays inch long: outermost involucral bracts smaller: akenes including 

 broad wing nearly orbicular in outline, half-inch in diameter. — Sk. ii. 462 ; Torr. & Gray, 

 Fl. ii. 279, excl. var. y. — W. Georgia to Louisiana and E. Texas. 



