92 



GENUS ARTEMISIA. 



maintained as separate subspecies only with the greatest difficulty. The widely branch- 

 ing inflorescence and fewer-flowered heads make redolens an easily recognized unit, but 

 these features may be only the result of the habitat, since it is thus far known only from 

 the proximity of clififs in northern Mexico. Because of this wide geographic separation 

 from its nearest relatives, redolens may stand as a subspecies, at least until its ecology is 

 better understood. It was referred by Gray to the section Dracunculus, an error which 

 has been already pointed out by Rydberg (N. Am. Fl. 34:278, 1916). Another derivative 

 of the discolor group is subspecies flodmani. This is a local form confined to western 

 Montana and adjacent States. The upper surface of its leaves has taken on a heavy 

 tomentum and the flowers in each head have been reduced in number. 



Fio. 11. 



Leaves of ATtemiaia vulgaris dis- 

 color: a, from near the base of the 

 stem, b, c, d, from toward the summit 

 of the same plant. Yosemite National 

 Park (73969 UC). This is the "in- 

 compta" form, also known as A. 

 underwoodi. All X 0.8. 



In its early southward migration, the subspecies tilesi, which is here considered as the 

 progenitor of all the other native American forms, underwent modification in a number of 

 its characters. Thus, through a simphfication in the cut of the leaf, together with some 

 reduction in the leaf-size and in the size of the heads, there was evolved the more southerly 

 subspecies heterophylla. This has been variously known as A. hookeriana Besser (1833), 

 A. douglasiana Besser (1833), A. vulgaris var. californica Besser (1841), and A. hetero- 

 phylla Nuttall (1841). The last is here chosen for the subspecific name as being the most 

 descriptive and the one in most general use. Forms connecting heterophylla with 

 tilesi are common where the geographical ranges of the two overlap in southern Canada 

 and adjacent United States. In this area are found specimens of tilesi with leaves only 

 once-pinnatifid and others in which the size of heads, foliage characters, and habit are 

 such that they might be classed as either the one or the other. The overlapping in the 

 size of the heads and in the number of flowers per head is brought out in table 6. The 

 types of heterophylla came from somewhere in Canada and were probably low plants with 

 pinnatifid leaves. It is unfortunate that the types were from near the border of the area 

 of distribution, since they do not well represent the normal form so common farther 

 south, especially from Washington to California. However, leaf-tracings and a single 

 head taken from the types and preserved at the New York Botanical Garden can be 

 easily duplicated in California. 



Subspecies heterophylla is comparatively rare in the northern Rocky Mountain States 

 and entirely wanting to the south of them, but to the west it swings across Washington 

 nearly to the coast, is abundant in Oregon and California, and extends on southward 

 into Lower California. Because of their more nearly entire leaves, these southern plants 

 recently have been referred to "A. douglasiana Lindley," the type of which came from 

 the Columbia River. This form, however, is scarcely distinguishable except in the her- 

 barium, where specimens frequently exhibit only the upper leaves. Field studies indi- 

 cate that the lower leaves are probably never entire. It must be said, however, that 

 southern specimens are likely to have a larger number of entire or only toothed leaves 



