212 COMPOSITE, (composite family.) 



sected leaves, and inconspicuous greenish or whitish flowers. ('A/i/Spocria, tha 

 food of the gods, an ill-chosen name for these worthless and coarse weeds.) 



5 1. Sterile heads sessile, crowded in a dense cylindrical spike, the top-shaped involucre 

 with the truncate margin extended on one side into a large, lancedate, hooded, 

 recurved, hristly-hairy tooth or appendage ; fertile involucre oblong and 4-angled. 



1. A. bidentata, Michx. Hairy (l°-3°high), yery leafy; leaves al- 

 ternate, lanceolate, partly clasping, nearly entire, except a short lobe or tooth 

 on each side near the base. (J) — Prairies of Illinois and southward. Aug. 



§ 2. Sterile heads in single or panicled racemes or spikes, the involucre regular. 

 # Leaves opposite, only lobed: sterile involucre 3-ribbed on one side. 



2. A. trifida, L. (Gbeat Eagweed.) Stem square, stout (4° -12° 

 high), rough-hairy, as are the large deeply 3-lobed leaves, the lobes oval-lanceo- 

 late and serrate ; petioles margined ; fruit obovate, 6-ribbed and tubercled. ® 

 — Var. INTEGKIF6HA is only a smaller form, with the upper leaves or all of 

 them undivided, ovate or oval. — Moist river-banks ; common. Aug. 



* * Leaves many of them alternate, once or twice pinnatifid. 



3. A. artemisiaefolia, L. (Roman Wormwood. Hog-weed. Bit- 

 tee-weed.) Much branched (l°-3° high), hairy or roughish-pubescent ; 

 leaves thin, twieepinrwiifid, smoothish above, paler or hoary beneath ; fruit obo- 

 void or globular, armed with about 6 short acute teeth or spines. ® — Waste 

 places everywhere. July -Sept. — An extremely variable weed, with finely 

 cut leaves, embracing several nominal species. 



4. A. psilostalchya, DC. Paniculate-branched (2° -5° high), rough 

 and somewhat hoary with short hispid hairs ; leaves once pinnatifid, thickish, the 

 lobes acute, those of the lower leaves often incised ; fruit obovoid, without tuber- 

 cles or with very small ones, pubescent, (l) (A. coronopifolia, Torr. ^ Gr.) — 

 Prairies and plains, Elinois and southwestward. Aug. 



31. XANTHIUM, Tourn. Cocklebue. Clotbue. 



Sterile and fertile flowers occupying different heads on the same plant ; the 

 latter clustered below, the former in short spikes or racemes above. Sterile 

 involucres and flowers as in Ambrosia, but the scales separate. Fertile invo- 

 lucre closed, coriaceous, ovoid or oblong, clothed with hooked prickles so as to 

 form a rough bur, 2-celled, 2-flowered ; the flowers consisting of a pistil with a 

 slender thread-form corolla. Achenia oblong, flat ; destitute of pappus. — 

 Coarse and vile weeds, with annual roots, low and branching stout stems, and 

 alternate toothed or lobed petioled leaves. (Name from ^dvdos, yellow, in allu- 

 sion to the color the plants are said to yield.) 



1. X. strumariiiin, L. (Common Cocklebur.) Rough; stems un- 

 armed; leaves dilated-triangular and more or less heart-shaped, on long petioles, 

 toothed and cut or obscurely lobed; fruit oval or oblong (^'-f long), pubes- 

 cent on the lower part of and between the hooked prickles, and with two strong 

 and usually straight beah at the summit. — Barn-yards, &c. (Nat. from Eu ) — • 

 Varies into forms with more spotted stems, and often larger fruit (|'- 1' long). 



