COMPOSITE FAMILY. 243 



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

 and S. 



-t- +- The slender smooth floicering stems (4°-10° high) leafy only near 

 the basp, divf(li)ig 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'3-2° long, besides the slender petiole, the margins somewhat toothed. 

 Ohio, W. 



S. comp6situm, 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 S or 4 along the terete stems, 

 rather small, entire or coarsely toothed. 



S. trifoli^tum, Linn. Stem smooth, often glaucous, 4°-6° high ; leaves 

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



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

 heads fewer and larger. Va., S. 



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



S. integrif61ium, Michx. Roughish, 2°-4° high, with terete stem and 

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

 and S. 



S. perfoliitum, Linn. Cup Plant. Very smooth square stems 4°-9° 

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

 which hold water fi'om the rains. Mich., W. and S. 



30. PARTHENIUM. (Greek: virgin, of no application.) 2/ (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. iVA, MARSH ELDER. (Name unexplained.) (p. 223.) Our 



commonest species is 



I. frut^Bcens, 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. trlfida, 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 5 

 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. 



