Vol. III.] 

 3 



RAGWEED FAMILY. 



297 



Woolly Gaertneria. 



Gaertneria tomentosa (A. Gray) Kuntze 



(Fig. 3597-) 



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

 4: 80. 1849. 



Gaertneria tomentosa 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. 



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 staminate ones capitate- 

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

 involucre of 1 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-cleft, 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. 1. X. 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. strumarium. 



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



i. Xanthium spinosum L. Spiny 

 or Thorny Clotbur, Clotweed 

 or Burweed. (Fig. 3598.) 



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



Stem pubescent or puberulent, much 

 branched, ascending or erect, i-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 2 // in 

 diameter, pubescent, armed with short 

 subulate rather inconspicuous beaks, and 

 numerous glabrous spines about l // 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. 



