COMPOSITE FAMILY. 243 



pinnatifid root leaves (of ovate outline) incline to present their edges N. 



and S. 



i- 4- The slender smooth flowering stems (4-10 high} leafy only near 

 the base, dividing above into a panicle of many smaller heads. 



S. terebinthinaceum, Linn. PRAIRIE DOCK, so called from the 

 appearance of the large root leaves, which are ovate or heart-oblong and 

 l-2 long, besides the slender petiole, the margins somewhat toothed. 

 Ohio, W. 



S. compdsitum, Michx. More slender and smaller, with round heart- 

 shaped leaves either toothed or cut, or divided. N. C., S. 



* * Leaves, or many of them, in whorls of 3 or 4 along the terete stems, 

 rather small, entire or coarsely toothed. 



8. trifoliatum, Linn. Stem smooth, often glaucous, 4-6 high ; leaves 

 lanceolate and entire or nearly so, roughish ; heads small. S. and W. 



S. Asterfscus, Linn. Rough-hairy ; leaves usually coarsely toothed ; 

 heads fewer and larger. Va., S. 



* * # Leaves opposite and clasping or connate ; stems leafy to the top. 



8. integrifdlium, Michx. Roughish, 2-4 high, with terete stem and 

 lance-ovate, partly heart-shaped, and entire, distinct leaves. Mich. W. 

 and S. 



8. perfoliatum, Linn. COP PLANT. Very smooth square stems 4-9 

 high, around which the ovate, coarsely toothed leaves are connate into cups 

 which hold water from the rains. Mich., W. and S. 



30. PARTHENIUM. (Greek: virgin, of no application.) "U (p. 



227.) 



P. integrif6lium, Linn. A coarse, rough plant, l-4 high, with 

 alternate, oblong or oval, crenate-toothed leaves (the lower cut-lobed), 

 and small whitish heads in a flat and dense corymb. Dry soil, Md. to 

 Minn, and S. 



31. IV A, MARSH ELDER. (Name unexplained.) (p. 223.) Our 

 commonest species is 



I. frut^scens, Linn. Nearly smooth, shrubby at the base, 3-8 ; 

 leaves oval or lanceolate, coarsely toothed, fleshy ; greenish-white heads 

 axillary and forming a leafy panicled raceme. Salt coast marshes, 

 Mass., S. 



32. AMBROSIA, RAGWEED. (The classical name.) (p. 222.) 

 Flowers greenish, all summer and autumn. 



* Leaves all opposite. 



A. trffida, Linn. Tall, coarse herb along low borders of streams; 

 4-10 high, rough ; leaves deeply 3-lobed on margined petioles, the 

 lobes lance-ovate and serrate ; staminate heads in racemes, their in- 

 volucres 3-ribbed on one side, the fertile one or fruit obovate and with 6 

 or 6 ribs ending in a tubercle or spiny point. 



* * Some or all the leaves alternate. 



A. bidentata, Michx. Hairy, l-3 high, very leafy; leaves alter- 

 nate, closely sessile, lanceolate, and with a short lobe or tooth on one 

 side near the base ; heads in a dense spike, the top-shaped involucre of 

 the sterile ones with a large lanceolate appendage on one side. Prairies, 

 111., S. and W. 



