296 



AMBROSIACEAE. 



[Vol. III. 



3. GAERTNERIA Med. Act. Pal. 3: 244. 1785. 

 [Fran.skria Cav. Icon. 2: 78. pi. 200. 1793.] 

 Hispid or tomentose branching herbs, with the aspect of Aiiibrosias, sometimes woody at 

 the base, with mostly alternate lobed or divided leaves, and small monoecious greenish heads 

 of discoid flowers, the staminate in terminal spikes or racemes, tUe pistillate solitary or clus- 

 tered in the upper axils. Involucre of the pistillate heads ovoid or globose, closed, 1-4- 

 celled, 1-4-beaked, armed with several rows of spines and forming a bur in fruit; corolla 

 none or rudimentary; style deeply bifid, its branches exserted; stamens none; achenes obo- 

 void, thick, solitary in the cells; pappus none. Staminate heads sessile, or short-peduncled, 

 their involucres broadly hemispheric, open, 5-12-lobed; receptacle chaffy; corolla regular, the 

 tube short, the limb 5-lobed; style undivided; anthers scarcely coherent; mucronate-tipped. 

 [In honor of Joseph Gaertner, 1732-1791, German botanist.] 



About 15 species, natives of America. In addition to the following, some 8 others occur in the 

 western and southwestern United States. 



Plant hirsute; annual; spines of the fruiting involucre long, flat. i. G. acantliicar[>a. 

 Leaves densely whitetomentose beneath; spines short, conic; perennials. 



Leaves bipinnatifid. 2. G. discolor. 



Leaves pinnately divided, the terminal segment large. 3. G. tomenlosa. 



I. Gaertneria acanthicarpa (Hook.) 



Britton. Hooker's Gaertneria. 



(Fig- 3595-) 



Ambrosia acanthicarpa Hook. Fl. Bor. .\m. i: 



309. 1833. 

 Franseria Hookeriana Nutt. Trans. Am. Phil. 



800.(11)7:345. 1841. 

 Gaertneria acanthicarpa Britton, Mem. Torr. 



Club, 5: 332. 1894. 



Annual, erect or diffuse, paniculatelj- 

 branched, i°-2° high; stem hirsute or hispid. 

 Lower and basal leaves slender-petioled, bi- 

 pinnatifid, 2'-4' long, the upper shortpetioled 

 or sessile, once pinnatifid, or merely lobed; 

 racemes of sterile heads usually numerous, 

 i'-3' long; fruiting involucres clustered in 

 the axils, 3"-4" long, commonly i-flowered, 

 armed with numerous long flat straight spines. 



In moist soil. Northwest Territory to western 

 Nebraska and Texas, west to British Columbia 

 and California. July-Sept. 



2. Gaertneria discolor (Nutt.) Kuntze. 



White-leaved Gaertneria. 



(Fig- 3596.) 



Franseria discolor Nutt. Trans. Am. Phil. Soc. 

 (11)7: 345. 1841. 



Gaertneria rf/jco/or Kuntze, Rev. Gen. PI. 339. 1S91. 



Erect or ascending from perennial rootstocks, 

 branched, about 1° high. Leaves nearly all bi- 

 pinnatifid, petioled, densely white-tomentose 

 beneath, green and pubescent or glabrate above, 

 2'-5' long; sterile racemes narrow, commonly 

 solitary, i''-2'long; fruiting involucres clustered 

 in the axils, finely canescent, about 2" long, 

 mostly 2-flowered, armed with short sharp conic 

 spines. 



In dry soil, Nebraska to Wyoming, Colorado 

 and New Mexico. Aug. -Sept. 



