294 COMPOSITiE. Franseria. 



* * Annual. (Ambrosidium, Nutf) 



5. F. Hookerianh (Nutt.) : much branched, paniculate ; stem scabrous and 

 more or less hirsute ; leaves bipiiinatifid, with few oblong or somewhat linear 

 segments, strigose-canescent; racemes paniculate; sterile involucres 5-8- 

 cleft, 10-20-flowered ; tlie fructiferous involucre covered with (12 or more) 

 long and slender flatfish spreading spines. — F. Hookeriana & F. montana, 

 Nutt.! I. c. Ambrosia acanthicarpa. Hook. ! ji. Bor.-Am. 1. jj. 309. 



Saskatchawan to the Oregon River, Douglas! Drununond! and near the 

 sources of the Colorado of the West, Nuttall ! — Fertile portion of the racemes 

 often as long as the sterile, frecjuently leafy at the base and partly com- 

 pound. Sterile heads small, on filiform pedicels. 



82. XANTHIUM. Touim. inst. t. 252 ; Linn. ; Gcertn. fr. L 164 ; 

 Schkuhr, handh. t. 291 ; DC. I. c. 



Heads glomerate-spicate ; the sjiikes sterile at the summit. Sterile Fl. 

 numerous in subglobose heads ; the scales of the involucre distinct, in a sin- 

 gle series. Receptacle oblong or cylindraceous, chaffy. Stamens inserted 

 in the base of the short and dilated 5-toothed and somewhat hairy corolla : 

 anthers distinct, but connivent. Style abortive, undivided. Fertile Fl. two, 

 enclosed in a 2-celled ovoid or oblong coriaceous closed involucre, which is 

 clothed with hooked prickles and terminated by 1 or 2 stout beaks. Corolla 

 filiform. Stamens none. Branches of the style linear-filiform. Achenia 

 solitary in each cell of the involucre, oblong, flat. — Coarse annual weeds, 

 with branching stems, and alternate, petioled, lobed or toothed leaves. 



§ 1. Leaves cordate, lobed, incised, or toothed, with no spines at their base: 

 fructiferous involucre iiith 2 beaks. — Euxanthium, DC. 



1. X. strumarium (Linn.) : fructiferous involucre oval, somewhat pubes- 

 cent ; the beaks straight (appressed or spreading) ; leaves 3-5-lobed incise- 

 ly-toothed ; the lobes acute. — Linn. spec. {ed. 2) p. 1400 ,• Fl. Dan. t. 270 ; 

 Lam. ill. t. 765, /. 1 ; Engl. bot. t. 2544 ; DC. ! prodr. 5. 2^- 523. 



j3. Canadense: fructiferous involucre pubescent-scabrous, or at length 

 glabrous; the beaks straight or slightly incurved; stem usually spotted. 

 — X. majus Canadense, Herm. Lugd. p. 635 .'' X. elatius Americanum, 

 &c., Moris, hist. 3. p. 604. sect. 15. t. 2, f. 2 ? X. Canadense, Mill. diet, 

 no. 2 ? Hook. 4* Am. bot. Bcechey, p. 148. X. Carol, medium, Dill. Elth. 

 t. 321 ? e\cl. fig. 13-16. X. Americanum, Walt. Car. p. 231 ? X. macro- 

 carpon ji. glabratum, DC. I. c. X. strumarium, Michx. fi. 2. p. 182 ; 

 Eli. sk. 2. ^p. 479 ? 



Waste places, around barnyards, &c., apparently introduced. Also Key 

 West, Florida, Mr. Blodgctt! (with fruit a little smaller than the European 

 plant, the beaks appressed.) p. Fields, &c., Canada ! Northern and West- 

 ern States ! and probably in the Southern States. Also in California, Hook. 

 Sf Am. July-Sept. — The true X. strumarium is more or less naturalized ; 

 the var. /3. is probably indigenous, and perhaps a distinct species ; but we 

 can indicate no further characters to distinguish it. except that the fruit is in 

 general a little larger than in the European plant, and the leaves perhaps 

 less lobed. — Burr-weed. Cockle-burr. Clot-burr. 



2. X. echinatum (Murray) : fructiferous involucre oval, very densely 

 clothed with rigid slender prickles, which are strongly hispid, as well as the 



