A. VULGARIS. 



91 



differing only in the tomentum, recurs at a number of places in the species, as, for exam- 

 ple, between ludoviciana and gnaphalodes and also, but with the addition of other tenden- 

 cies, between discolor and flodmani. When the former pair is reached in this discussion, 

 evidence will be adduced for considering the heavily tomentose as the more advanced 

 type. 



Fio. 10. 

 Leaves of Artemisia vul- 

 garis typica and A. v tilesi: 

 a, typica from Rochester, 

 New York, August 16, 

 1897, House (Gr); 6, tilesi 

 from Dutch Harbor, Una- 

 laska. Van Dyke 101 (Gr). 

 Both X 0.5. 



Aside from tilesi itself, the subspecies thus'far considered have not led to other well- 

 marked variations, however numerous their minor forms may be. The remaining sub- 

 species, on the other hand, may be grouped around three central ones, each of which 

 has given rise to one or more groups of equal rank with itself. The first of these is 

 discolor, a common subspecies in the western mountainous districts. This is widely 

 separated from tilesi in most taxonomic treatments and is even placed in a separate sec- 

 tion of the genus in the latest monographic account (Rydberg, N. Am. Fl. 34:245, 1916). 

 Yet in all essential characters these two forms come very close to each other ; both have 

 short, twice-dissected leaves with the same peculiar cut to the lobes, the involucre is 

 green in both, and the heads, although averaging smaller in discolor, exhibit a complete 

 intergradation in this respect (see table 6). Thus the only characters left for the dis- 

 tinction of discolor are the usually smaller heads and the somewhat narrower lobes of the 

 smaller leaves. The connection seems to be estabUshed by specimens in which the heads 

 are large, but with all the other characteristics of discolor (Bear Canon, Custer County, 

 Idaho, Nelson and Macbride 1521). In the collection just cited the involucre is about 

 4 mm. high and 4.5 mm. broad and the number of disk-flowers varies from 23 to 29. For 

 some unexplained reason, A. v. discolor often has been confused with A. v. mexicana, but 

 this latter has exceptionally long leaves with slender, entire lobes and the heads are 

 usually smaller and more tomentose. The inflorescence of discolor is sometimes very 

 similar to that of A. v. lindleyana and the two are often confused in the absence of good 

 foUage. This subspecies seems to intergrade or hybridize also with subspecies gnapha- 

 lodes and ludoviciana, as is indicated by a series of specimens gathered near Durant, in 

 western Montana (Hall 11579 and 11580 UC). 



Indicated on the chart as a derivative of discolor, but of doubtful origin is the subspecies 

 redolens. If morphological characters alone were taken into account, the two could be 



