COMPOSITE FAMILY. 243 



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

 and S. 



■>- +- 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. 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 3 or 4 along the terete stems, 

 rather small, entire or coarsely toothed. 



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

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



S. Asterf sous, 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. integrifdlium, Michx. Roughish, 2°-4° high, with terete stem and 

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

 and S. 



S. perfoliatum, Linn. Cup 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. PARTHENTUM. (Greek: virgin, of no application.) % (p. 



227.) 



P. integrifdlium, 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. frute"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 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, 

 HI., S. and W. 



