COMPOSITE. (COMPOSITE FAMILY.) 251 



inate flowers, with slender chaff intermixed, or none. Anthers almost sepa- 

 rate. Fertile involucre (fruit) oblong or top-shaped, closed, pointed, resembling 

 an achenium, and usually with 4-8 tubercles or horns near the top in one row 

 enclosing a single flower which consists of a pistil only ; the elongated branches 

 of the style protruding. Achenia ovoid : pappus none. Homely and coarse 

 weeds, with opposite or alternate lobed or dissected leaves, and inconspicuous 

 greenish or whitish flowers, produced throughout late summer and autumn : our 

 species are all annuals. ( 'A/i/Spoo-t'a, the food of the gods, an ill-chosen name for 

 these miserable weeds.) 



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

 with its truncate margin extended on one side into a large, lanceolate, hooded, re- 

 curved, biistly-hairy tooth or appendage ; fertile involucre oblong and 4-angled. 



1. A. bidentata, Michx. Hairy ( 1- 3 high), very leafy ; leaves alter- 

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

 each side near the base. Prairies of Illinois and southward. 



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

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



2. A. trifida, L. (GREAT RAGWEED.) Stem stout (4 -12 high), rough- 

 hairy, as are the large deeply 3-lobed leaves, the lobes oval-lanceolate and 

 serrate ; petioles margined ; fruit obovate, 5 - 6-ribbed and tubercled. Var. 

 INTEGRIF6LIA is only a smaller form, with the upper leaves, or all of them, un- 

 divided, ovate or oval. Moist river-banks : common. 



# # Leaves many of them alternate, all once or twice pinnatifid. 



3. A. artemisisefblia, L. (ROMAN WORMWOOD. HOG-WEED. BIT- 

 TER-WEED.) Much branched (l-3 high), hairy or roughish-pubescent ; 

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

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

 everywhere. An extremely variable weed, with finely cut leaves ; rarely the 

 spikes bear all fertile heads. 



4. A. psilostachya, 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 tubercles or 

 with very small ones, pubescent. (A. coronopifolia, Torr. $* Gr.) Prairies and 

 plains, Wisconsin, Illinois, and south westward. 



31. XANTHIUM, Tourn. COCKLEBUR. CLOTBTJR. 



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

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

 volucres and flowers as in Ambrosia, but the scales separate. Fertile involucre 

 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 slen- 

 der 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 ; flowering in summer and autumn. (Name 

 from dvdos, yellow, in allusion to the color the plants are said to yield.) 



