384 ORDER LXVIII. C0MP0SITJ2. 



panicle ; staminate florets numerous, solitary at the summit of the 

 spike ; pistillate ones in small clusters at the base. Involucre of the 

 staminate florets 5 — 8-lobed, hairy. Corolla tubular. Involucre of the 

 fertile florets persistent, 5-lobed. Fruit with 6 spines. — Wliite. #. 

 Aug. — Sept. Common. 4 — 6 feet. Bitter-weed. 



2. A. ela'tior, (L.) Stem virgate, pubescent wlien young. Leaves 

 bipinnatifid, nearly glabrous ; petioles ciliate. Flowers in jjaniculate 

 racemes. Involucre of the staminate florets globular, soraewhat hairy; 

 fertile florets in small clusters. Kut with 6 short spines. — White. ®. 

 July — Sept. Middle, upper Car. and Geo. 4 — 8 feet. 



Hog-weed. Roman Wormwood. 



3. A. artemisi^fo'lia, (L.) Stem erect, slightlypubescent, fi\stigiately 

 branched. Leaves toward the base bipinnatifid, opposite ; those toward, 

 the summit pinnatifid, opposite, nearly glabrous on the upper surface, 

 pubescent beneath. Racemes terminal by threes. Involucre of the 

 staminate florets globular ; fertile florets axillary, sessile ; spines short. 

 — White. ©. Aug. — Sept. Mountains. 4 — 6 feet. 



4. A. panicula'ta, (Mich.) Stem, erect, paniculately branched, villous. 

 Leaves alternate toward the base, bipinnatifid toward the summit ; 

 segments all lanceolate-acute, pubescent. Flowers in terminal and ax- 

 illary racemes, the upper staminate, the lower fertile. Involucre of the 

 staminate florets 10-toothed, 10 flowered. Fruit muricate, clustered, 

 small, obovate. — White. @. July — i?ept. Cultivated grounds, very 

 common. 2 — 6 feet. 



Genus XL.— XA^"'TIIIUM. Tourn. 

 (From xanthos, yellow, from the color said to be produced on the hair by this plant.) 



Flowers monoecioiis. Staminate florets, involucre imbricate. 

 Anthers approximate, not united. Rece2)tacle chaliy. Fertile 

 florets. Involucre 2-leaved, 2-flowered. Corolla none. Drupe 

 dry, muricate, 2-cleft. Nut 2-celled. 



1. X. struma'rium, (L.) Stem erect, pubescent, scabrous, angled. 

 X<'rti'(?s alternate, cordate, usually 3-lobed. serrate, pubescent, very large, 

 on long petioles. Pistillate florets m axillary racemes; involucre con- 

 sisting of subulate leaves. Chaff subulate. Fertile florets at the base 

 of each raceme ; involucre 10-leaved, 2-flowered. Fruit eUiptic, pu- 

 bescent, armed with hooked bristles. — White. ®. July — Oct. Very 

 common. 3 — 6 feet. Cockle Bur. Clott Bur. Sheep Bur. 



2. X. echina'tum, (L.) Stem rough, spotted. Leaves broad, sub- 

 cordate, irregularly toothed, obscurely lobed. Involucre oval, with 

 rigid prickles. — Near salt water, Mass. — Car. Aug. — Oct. 1 — 2 feet. 



5. X. spiNo'suM, (L.) Stem pubescent, terete, with ternate spines 

 from each side of the petiole. Leaves alternate, 3-lobed, ovate-lanceo- 

 late, pubescent on the upper surface, tomentose beneath. Staminate 

 florets solitary, at the base of each spine ; involucre man}- leaved. Fer- 

 tile florets axillary, solitary. Fruit armed with short prickles. Fruit 

 2-celled. — White, %. July — Oct. Common along the coast. 3 — -5 

 feet. Prickly Clotweed. 



