296 



AMBROSIACEAE. 



[Vol. III. 



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

 [Franseria Cav. Icon. 2: 78. pi. 200. 1793.] 

 Hispid or tomentose branching herbs, with the aspect of Ambrosias, sometimes wood}- 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, the 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. 



Leaves densely white-tomentose beneath; spines short, conic; perennials. 



Leaves bipinnatifid. 



Leaves pinnately divided, the terminal segment large. 



i. G. acanthicarpa. 



2. G. discolor. 



3. G. tomentosa. 



i. Gaertneria acanthicarpa (Hook.) 



Britton. Hooker's Gaertneria. 



(Fig- 3595-) 



Ambrosia acanthicarpa Hook. Fl. Bor. Am. 1: 



309. 1833. 

 Franseria Hookeriana Nutt. Trans. Am. Phil. 



Soc. (II) 7:345- 1841. 

 Gaertneria acanthicarpa Britton, Mem. Torr. 



Club, 5: 332. 1894. 



Annual, erect or diffuse, paniculately 

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

 Lower and basal leaves slender-petioled, bi- 

 pinnatifid, 2 / -4 / long, the upper short-petioled 

 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. 

 (II) 7: 345. 1841. 



Gaertneria rf/jco/o?- Kuntze, Rev. Gen. PI. 339. 1891. 



Erect or ascending from perennial rootstocks, 

 branched, about i high. Leaves nearly all bi- 

 pinnatifid, petioled, densely white-tomentose 

 beneath, green and pubescent or glabrate above, 

 2 r -5 7 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, 

 and New Mexico. Aug. -Sept. 



Colorado 



