274 COMPOSITE. (COMPOSITE FAMILY.) 



44. XANTHIUM, Tourn. COCKLEBUR. CLOTBUR. 



Sterile and fertile flowers occupying different heads, the latter clustered 

 below, the former in short spikes or racemes above. Sterile involucres and 

 flowers as in Ambrosia, but the scales separate and receptacle cylindrical. 

 Fertile involucre closed, coriaceous, ovoid or oblong, clothed with hooked 

 prickles so as to form a rough bur, 2-celled, 2-flowered ; the flower consisting 

 of a pistil and slender thread-form corolla. Achenes 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 sum- 

 mer and autumn. (The Greek name of some plant that was used to dye the 

 hair yellow ; from av06s, yellow.) 



* Leaves attenuate to both ends, with triple spines at the base. 



X. SPiN6suM, L. (SPINY CLOTBUR.) Hoary-pubescent; stems slender, 

 with slender yellow 3-parted spines at the axils ; leaves lanceolate or ovate- 

 lanceolate, tapering to a short petiole, white-downy beneath, often 2 - 3-lobed 

 or cut ; fruit (' long) pointed with a single short beak. Waste places on the 

 sea-board and along rivers, Mass, and southward. (Nat. from Trop. Amer.) 



# * Leaves cordate or ovate, 3-nerved, dentate and often lobed, long-petiolate ; 

 axils unarmed ; fruit Z-beaked. 



X. STRUMA.RIUM, L. Low (1-2 high) ; fruit 6-8" long, glabrous or pu- 

 berulent, with usually straight beaks and rather slender spines. A weed of 

 barnyards, etc., sparingly nat. from Eu. (?) or Ind. (?). 



1. X. Canad^nse, Mill. Stouter, the stem often brown-punctate ; fruit 

 about 1' long, densely prickly and more or less hispid, the stout beaks usually 

 hooked or incurved. River-banks and waste places, common. Var. ECHI- 

 NA.TUM, Gray, usually low, with still denser and longer, conspicuously hirsute. 

 or hispid prickles. Sandy sea-shores and on the Great Lakes. 



45. TETRAGONOTHECA, Dill. 



Heads many-flowered, radiate; the rays 6-9, fertile. Involucre double* 

 the outer of 4 large and leafy ovate scales, united below by their margins intn 

 a 4-angled or winged cup ; the inner of small chaffy scales, as many as th 

 ray-flowers, and partly clasping their achenes. Receptacle convex or conical, 

 with narrow and membranaceous chaff. Achenes very thick and obovoid, flat 

 at the top; pappus none. Erect perennial herbs, with opposite coarsely 

 toothed leaves, their sessile bases sometimes connate, and large single heads 

 of pale yellow flowers, on terminal peduncles. (Name compounded of rerpd- 

 yavos, four-angled, and d'fjKrj, a case, from the shape of the involucre.) 



1. T. helianthoides, L. Villous and somewhat viscid, 1-2 high, 

 simple ; leaves ovate^or rhombic-oblong, sessile by a narrow base ; involucral 

 scales and rays about 1' long. Sandy soil, Va. and southward. June. 



46. ECLIPTA, L. 



Heads many-flowered, radiate ; rays short ; disk-flowers perfect, 4-toothed, 

 all fertile. Involucral scales 10-12, in 2 rows, leaf -like, ovate-lanceolate. 

 Receptacle flat, with almost bristle-form chaff. Achenes short, 3 - 4-sided, or 

 in the disk laterally flattened, roughened on the sides, hairy at the summit ; 

 pappus none, or an obscure denticulate crown. An annual rough herb, with 



