130 GENUS AKTEMISIA. 



22. ARTEMISIA FILIFOLIA Torrey, Ann. Lye. N. Y. 2:211, 1828. Plate 16. 

 Sand Sagebrush. 



A rounded shrub, 5 to 12 dm. high, mildly and pleasantly scented ; stems freely branched 

 throughout, the older parts with a close and smooth dark-gray or blackish bark, the 

 numerous slender twigs striate beneath a canescent pubescence; principal leaves sessile, 

 often with fascicled ones in their axils, filiform, 3 to 8 cm. long, less than 0.5 mm. wide 

 at base, ternately divided into long filiform divisions or some of them entire, canescent ; 

 upper leaves but little reduced, more often entire, ascending or incurved, canescent; 

 inflorescence a narrow, dense, leafy panicle, 10 to 30 cm. long by 1 to 5 cm. broad; 

 heads heterogamous, crowded, nodding on recurved peduncles; involucre subglobose, 

 1.5 to 2 mm. high and nearly as broad; bracts 5 to 9, the outer ones short and thick, the 

 inner ones thinner, broadly elliptic, obtuse, all densely canescent on exposed parts, none 

 scarious; receptacle smooth and naked; raj^-flowers 2 or 3, fertile, corolla tubular, about 

 1 mm. long; disk-flowers 1 to 6, sterile, corolla broadly funnelform, 5-toothed, 1.5 to 2 

 mm. long, resinous-glandular; style of disk-flowers 1 to 1.5 mm. long, either cup-shaped 

 at the erose summit, the branches being entirely fused, or shortly bifid and the lobes 

 with erose margins ; achenes ellipsoid, narrowed to the corolla, either smooth or with 4 or 5 

 raised ribs, glabrous, those of the disk-flowers abortive. 



Wyoming and western Nebraska to Texas, Chihuahua, Arizona, Nevada, and Utah. 

 Type locality not given. Collections: Uva, Laramie County, Wyoming, Nelson 8636 

 (Gr, NY, UC); North Denver, Colorado, Eastwood 32 (Gr, UC, many of the heads 

 transformed into galls) ; Deuel County, western Nebraska, Rydberg 206 (NY) ; Tribune, 

 Greeley County, Kansas, September 18, 1893, Reed (UC); near Alva, Oklahoma 

 (common) Stevens 2811 (Gr); Box Springs, Texas, Tracy 8155 (NY); near Del Norte, 

 Chihuahua, Pringle 770 (Gr, NY, UC, US) ; Mesilla Valley, Dona Ana County, New 

 Mexico, October 2, 1889, Wooton (UC, many of the heads transformed into galls); 

 Willcox Flat, southeastern Arizona, Shreve J^257 (SF, UC) ; above Rioville, southeastern 

 Nevada, Jones 5036 (UC); between Kanab and Carmel, Utah, Jones 60Jt7 (NY, UC). 



MINOR VARIATION. 



1. Artemisia plattensis Nuttall, Trans. Am. Phil. Soc. II, 7:397, \?A\.—A. Jilijolia. Separated from A. 

 filifolia only on its inflorescence, which is described as a loose and regularly simple-branched panicle. All 

 degrees of density of inflorescence may be observed in a field of these plants. Type locality, upper plains of 

 the Platte River. 



RELATIONSHIPS. 



The only American Artemisia which can claim close relationship is A. pedatifida, 

 as will be pointed out under that species. In the opinion of Rydberg, these two are 

 suflBciently well set-off from the other species of his subgenus Dracunculus to form a 

 separate section. This he distinguishes by the shrubby or subshrubby habit and the 

 "usually more or less 2-cleft" style of the disk-flowers (N. Am. Fl. 34:245, 1916). 

 This cleavage of the style is fairly well marked in the specimens examined of pedatifida, 

 although even in this species there is a partial fusion in some cases, but in filifolia it is 

 often obscure and sometimes it fails entirely. Since species of Rydberg's section with 

 entire styles, particularly campestris, also have evident branches in somewhat over 30 

 per cent of the flowers examined, this feature is seen to be too variable to be of much 

 real value as a specific or sectional criterion. It is, however, of great assistance in 

 working out the phylogeny of the species of this group. For example, since the original 

 condition undoubtedly was one in which the branches were distinct for some distance, 

 entire styles are to be looked upon as the result of fusion of these branches and therefore 

 as representing a more advanced type of plant. According to this view, A. filifolia 

 is intermediate in its development, for, while its style is usually branched, in some cases 

 the parts are completely fused and terminated by an unbroken cup-like border (e. g., 



