A. FILIFOLIA — A. PEDATIFIDA. 131 



plants from Canon City, Colorado, August 30, 1919, Hall). This allies it with A. 

 campestris and A. pedatijida, which are also in a transitory stage as regards this character, 

 and places it below A. dracunculus, in which the branches are usually completely fused. 

 This last species, however, is less highly developed in certain other particulars, such as 

 the herbaceous habit, and is therefore provisionally retained first in the sequence of 

 species. The results of a detailed examination of style-branches are given in the intro- 

 ductory remarks on criteria (p. 38). 



In comparing A. filifolia with species outside its own section, one is impressed with 

 the remarkable similarity to A. calif omica. This extends to the habit, foliage, inflores- 

 cence, and ecologic behavior. If such a relationship exists, calif omica is obviously the 

 more primitive, chiefly because of its fertile disk-achenes, larger number of flowers in 

 the head, and evidently closer connection with the genus Crossostephium. The deriva- 

 tion of filifolia would involve a considerable reduction in the number of flowers, an 

 abortion of the central achenes, and the rounding of the summit of the ray-achenes, 

 as well as the smoothing out of the angles of these latter. It is also to be noted that in 

 A. calif arnica there is no tendency toward a fusion of the style branches. Therefore, 

 while this connection is considered as possible, it is not demonstrable with the evidence 

 now at hand. 



ECOLOGY. 



Artemisia filifolia resembles both A. iridentata and calif arnica in life-form, but is more 

 like the latter in its rounded bushy habit. It is typically a subclimax dominant of sandy 

 soils, and perhaps the most widespread shrub on inland dunes and sandhills from 

 Nebraska to Arizona. In the north especially it often forms pure consocies, but south- 

 ward it is usually associated with Yticca, Chrysothamnus, Dalea scoparia, PoUomintha 

 incana, or Atriplex canescens. Toward the close of the succession, the sand sagebrush 

 persists for a long time in the mixed prairie cover, producing the appearance of a savan- 

 nah. It is one of the most characteristic indicators of sand, and changes in abundance 

 serve to denote the amount of sand in the soil. The heads are often enlarged and trans- 

 formed into galls by species of Rhopalomya. 



USES. 

 The value of the sand sagebrush as a browse shrub depends upon the region where it 

 grows. In the grassland districts it is seldom much eaten, because of the abundance of 

 other food. Thus it is reported from Texas and the Rocky Mountain States north to the 

 Dakotas as of little value, and the normal development of the plants verifies this state- 

 ment. But in the more arid southwest, particularly New Mexico and Arizona, the plant 

 is reported to be of considerable value, and the closely cropped, irregular shrubs give 

 evidence of close browsing. In the last-named State it is of importance only in the 

 eastern part, since it becomes sparse toward the west and is entirely wanting as the 

 California line is approached. Attention should be given to this species as a cause of 

 hay-fever, since it possesses all of the necessary characteristics and is fairly common near 

 settled districts, especially in eastern Colorado. 



23. ARTEMISIA PEDATIFIDA Nuttall, Trans. Am. Phil. See. II, 7:399, 1841. Plate 16. 

 BiRDFOOT Sagebrush. 



A low perennial subshrub with a tough woody root, 0.5 to 1.5 dm. high, the odor 

 unknown; stems numerous, erect from the short woody base (this with fibrous exfoliating 

 bark), obscurely striate, cinereous-pubescent; basal leaves tufted, petioled, 1 to 2 cm. 

 long including the petiole and nearly as wide across the lobes, once or twice ternately 

 divided into narrowly spatulate or nearly linear short divisions, gray with a fine dense 

 pubescence; upper leaves smaller, with few divisions or entire, permanently cinereous 



