COMPOSITE FAMILY. 201 



49. POLT^MNIA, LEAF-CUP. (These coarse and inelegant plants are 

 oddly dedicated to one of the Muses. ) Fl. summer and autumn. Jl 



P. Canadensis, common in shaded ravines N., is 3° - 5° high, clammy- 

 hairy, with thin leaves, the lower pinnatifid, the upper 3 - 5-lobed or angled, 

 and the few pale-yellow and broad rays of the small heads shorter than the 

 involucre. 



P. Uved^ia, in rich soil from New York to 111. and S., is roughish-hairyj 

 stout, 4° -10° high, with large ovate and angled or lobed leaves, the upper 

 ones sessile, and rays of the pretty large head 10-15, bright yellow, longer than 

 the involucre. 



50. SILPHIUM, ROSIN-PLANT. (Ancient Greek name of some very 

 diiferent plant. ) Fl. summer and autumn. ^ 



§ 1. Leaves alternate, large, most of them petioled. 

 « The stout and rough flowering stems ( 3° - 6° high) leafy up to the few large heads : 

 scales of involucre ovate, vxith tapering and spreading rigid tips. 



S. lacini&tam, Rosin-Weed or Compass-Plant, of prairies, from Michi- 

 gan W. & S., so called because the rough-hairy deeply pinnatifid root-leaves (of 

 ovate outline) incline to present their edges N^ & S. 



» ♦ The slender smooth flowering stems (4° - 10° high) leafy only near the hose, 

 dividing above into a panicle of many smaller heads. 



S. terebinthin^eum, Pkaieie-Dook, so called from the appearance 

 of the large root-leaves, which are ovate or heart-oblong and 1° - 2° long, besides 

 the slender petiole, the margins somewhat toothed : common W. 



S. compdsitum, from North Carolina S., is more slender and smaller, with 

 round heart-shaped leaves either toothed or cut, or divided. 



§ 2. Leaves or many of them in whorls of S or 4 along the terete stems, rather small, 



entire or coarsely toothed. 

 S. trifoli^tum, of S. & "W., has the smooth stem 4°-6° high, lanceolate 

 roughish leaves, and small heads. 

 S. Asteriscus, of dry soil S., is rough-hairy, with fewer and larger heads. 



§ 3. Leaves opposite and clasping or connate : stems leafy to the top. 



S. inteerifblium, in prairies from Michigan W. & S. ; roughish, 2° - 4° 

 high, withlance-ovate partly heart-shaped and entire distinct leaves. 



S. perfoli&tum, Cup-Plant, of rich soil W. & S. : with very smooth 

 square stems 4° - 9° high, around which the ovate coarsely toothed leaves are 

 connate into cup which holds water from the rains. 



51. DAHLIA. (Named for a Swedish professor, Dahl, contemporary with 

 Linnaeus.) y. Two or three Mexican species, of which the most familiar is 

 D. variabilis, Common Dahlia of the gardens, with pinnate leaves, ovate 



serrate leaflets, and large heads, much increased in size and altered, of all colors : 

 roots fascicled and tuberous (Lessons, p. 35, fig. 87). 



52. COREOPSIS, TICKSEED. (Named from Greek word for bug, from 

 the shape of the akenes. ) Many wild species : several cult, for ornament : these 

 are the commonest. Fl. summer. ( See Lessons, p. 94, fig. 268, 269.) 



§ 1. Bays broad, coarsely 3 - 5-toothed : outer involucre not longer than the inner : 

 alcenes orbicular or oval, incurved when mature. Chiefly cultivated. 



* ® (D Disk-flowers and lower part of the rays darJc-colored or brown-purple : 

 akenes in these species wingless and nearly naked at top : leaves compound. 



C. tinetbria, of Arkansas, &c., the commonest Coreopsis or Calliopsis 

 of all country gardens ; smooth, with lower leaves twice-pinnately divided into 

 narrow leaflets, numerous heads, and lower half or sometimes almost the whole 

 of rays brown-purple : in one variety they are changed to tubes. 



