Vol. hi.] 



RAGWEED FAMILY. 



297 



3. Gaertneria tomentosa (A. Gray) Kuntze 

 (Fig. 3597-) 



Franseria lomenlosa A. Gray, Mem. Am. Acad. 

 4: 80. 1849. 



Gaertneria lomenlosa Kuntze, Rev. Gen. PI. 339. 

 1891. 



Erect from a deep perennial root, usually 

 branched at the base, i°-3° high. Leaves pin- 

 nately lobed or divided, finely and densely to- 

 mentose on both sides, or ashy above, the ter- 

 minal segment lanceolate or oblong-lanceolate, 

 acuminate, serrulate or entire, very much larger 

 than the 2-6 rather distant narrow lateral ones; 

 sterile racemes solitary, 2'-4' long; fruiting in- 

 volucres solitary, or 2-3 together in the upper 

 axils, ovoid, finely canescent or glabrate, 2- 

 flowered, about 3" long, armed with subulate- 

 conic, very acute, sometimes curved spines. 



On rich prairies and along rivers, western Ne- 

 braska, Kansas and Colorado. Aug. -Sept, 



Woolly Gaertneria. 



4. XANTHIUM L. Sp. PI. 987. 1753. 



Monoecious annual branching coarse rough or spiny herbs, with alternate lobed or den- 

 tate leaves, and rather small heads of greenish discoid flowers, the staininate ones capitate- 

 clustered at the ends of the branches, the pistillate axillary. Staminate heads with a short 

 involucre of i to 3 series of distinct bracts; receptacle cylindric, chaffy; corollas tubular, 5- 

 toothed; anthers not coherent, mucronate at the apex; filaments monadelphous; style slen- 

 der, undivided. Pistillate heads of an ovoid or oblong, closed involucre, covered with hooked 

 spines, 1-2-beaked, 2-celled, each cavity containing one obovoid or oblong achene; corolla 

 none; pappus none; style 2-cIeft, its branches exserted. [Greek, yellow, from its yielding 

 a yellow hair-dye.] 



About 5 species (more according to some authors), of wide geographic distribution. 



Leaves lanceolate, not cordate; axils bearing 3-divided spines. i. .V. spinosum. 



Leaves orbicular or broadly ovate, cordate, or truncate; axils not spiny. 



Bur 6"-9" long, usually nearly glabrous; beaks nearly straight; introduced. 2. X. siriimariuiii. 



Bur9"-i2" long, hispid-pubescent; beaks hooked or incurved; native. 3. -V. Canadense. 



I. Xanthium spinosum L. Spiny 



or Thorny Clotbur, Clotweed 



or Burweed. (Fig. 3598.) 



Xanlhiiini spinosum L- Sp. PI. 987. 1753. 



Stem pubescent or puberulent, much 

 branched, ascending or erect, l°-3° high- 

 Leaves lanceolate or ovate-lanceolate, acute 

 or acuminate, lobed, or the upper entire, 

 narrowed at the base, short-petioled, white- 

 canescent beneath and on the whitish veins 

 of the upper surface, 2'-5' long; axils each 

 ■with a short-stalked 3-pronged yellow spine 

 nearly i' long; ripe fertile involucre (bur) 

 oblong-cylindric, 4"-6" long, about 1" in 

 diameter, pubescent, armed with short 

 subvilate rather inconspicuous beaks, and 

 numerous glabrous spines about \" long. 



In waste grounds, Ontario to Florida, west to 

 Illinois, West Virginia, Missouri and Texas. 

 Widely distributed as a weed in western and 

 tropical America, Naturalized from Europe 

 or Asia. Aug. -Nov. 



