COMrOSITE FAMILV. 243 



Iiimiatiful root leaves (nf ovate outline) incline to present their edges N. 

 and y. 



-t- -t- The slender i^monlh jhivcrwfi stems (4^-10° high) leafij only near 

 the base, diviiluKj 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 soniewliat 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 alonr; the terete stems, 

 rather small, entire or coarsely toothed. 



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

 lanceohitt' anil entire or nearly so, roughish ; heads small. S. and W. 



S. Asterisciis, Linn. Hough-hairy ; leaves usually coarsely toothed ; 

 heads fewer and larger. Va., S. 



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



S. integrif6lium, Michx. Roughish, 2°-4'^ high, with terete stem and 

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

 and S. 



S. perfoli^tum, 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. PARTHENIUM. (Greek: virr/in, of no application.) 2i (p. 



P. integrif61ium, Linn. A coarse, rough plant, l°-4° high, witli 

 alternate.', ohlung or oval, crenate-toothed leaves (tlie 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. 22.3.) Our 

 commonest species is 



I. fnit^scens, Linn. Nearly smooth, shrubby at the base, o^"-8° ; 

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

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



Mass., S. 



32. AMBROSIA, RAGWEED. (The cla.ssical name.) (p. 222.) 

 Flowers greenish, all summer and autumn. 



* Leaves all opposite. 



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

 .l'-_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, closi'ly sessile, lanceolate, and with a short lobe or tooth on one 

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

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

 111., S. and W. 



