106 GENUS ARTEMISIA. 



pears as the grama sod becomes close. It mixes more or less with A. tridentata, Chryso- 

 thamnus nauseosus junceus, Atriplex confertifoUa, and especially Gutierrezia sarothrae. 

 This species is an indicator of somewhat less xerophytic conditions, particularly in 

 consequence of less competition, and is to be regarded as a relict in the drier grassland 

 areas. It doubtless owes its form largely to grazing, and overgrazing of the grasses 

 causes it to persist in the climax where it would otherwise disappear. 



The foliage is more palatable to stock than that of the common sagebrush. The 

 taste is less bitter, the odor less strong, and the slender, leafy twigs are less woody. 

 It is browsed in preference to other shrulas in the regions where it grows and is reported 

 by grazing examiners as "very good." Over much of its distributional area, however, 

 the plants are not sufficiently abundant to add largely to the value of the range. It is of 

 greatest importance in northern Arizona and northern New Mexico. 



Section II. ABSINTHIUM. 

 Phylogeny of the Species. 

 The species which gives its name to this section occurs in America only as an introduc- 

 tion and is not directly connected with the others. The remaining three are of one stock, 

 and apparently stand in direct relation to one another. The ancestral form was quite 

 certainly a perennial Siberian or at least Arctic herb. The development of a subshrubby 

 habit and dissected foliage resulted in A. frigida, which spread out over Eurasia in a 

 variety of forms and also invaded North America, occupying large areas on the plains 

 and foothills as far south as Texas and Arizona. From this developed scopulorum and 

 pattersoni, which came to occupy the higher altitudes in the mountains of western North 

 America, where they are now widely isolated from all of their relatives except frigida. 

 They retained the herbaceous habit, but the inflorescence was so narrowed as to become 

 scarcely more than a raceme. A. pattersoni apparently arose directly from scopulorum 

 in response to more intense alpine conditions. A. rupestris does not occur in America, 

 but is inserted in the chart, since possibly it represents the ancestor of frigida. It is 

 probable, however, that evolution has developed in the opposite direction, that is, 

 rupestris arose through the loss of pubescence. The detailed statistics and other data 

 from which the above conclusions have been drawn are given in the paragraphs on 

 relationships that accompany each of the species in the following account. 



16. ARTEMISIA ABSINTHIUM Linnaeus, Sp. PI. 848, 1753. Plate 11. Absinthe 

 Sage WORT. 



A perennial herb, but sometimes slightly woody at base, 4 to 10 dm. high, very fragrant; 

 stems clustered, simple below, erect, striate, thinly cinereous or glabrate and then 

 commonly reddish; basal leaves long-petioled, rounded-ovate in outline, 3 to 5 cm. long 

 in addition to the petiole, 2 or 3 times pinnately parted into oblong or oblanceolate 

 obtuse often toothed lobes, silky-canescent, sometimes less so on the upper side; upper 

 leaves with fewer lobes and these mostly lanceolate and acute, those of the inflorescence 

 from parted to merely cleft or entire and sessile, all silky like the lower; inflorescence a 

 profuse leafy panicle with straight ascending branches, 15 to 40 cm. long, 5 to 20 cm. 

 broad, occasionally much narrowed, the tips of the branches extending beyond the 

 leaves; heads heterogamous, short-peduncled, nodding; involucre hemispheric, 2 to 3 

 mm. high, 3 to 4 mm. broad; bracts 12 to 18, the outer linear, the inner broadly elliptic 

 and obtuse, all canescent, but the inner with broad scarious margins; receptacle covered 

 with long white hairs; ray-flowers 9 to 20, fertile, corolla 1.5 mm. long, obliquely short- 



