A. VULGARIS. 89 



RELATIONSHIPS. 



The species of Artemisia most closely related to A. vulgaris are indicated on the chart 

 (fig. 9). A. alaskana, A. franserioides, and A. stelleriana, although assembled close 

 to vulgaris in the diagram, are believed not to be directly concerned with its origin, 

 since these species represent divergent phylogenetic lines. None of them indicate any 

 tendency towards intergradation with the forms now under consideration. On the other 

 hand, the group consisting of ^4. parryi, A. macrobolrys, A. norvegica, and A. senjavinensis 

 seems to have had an origin very close to that of vulgaris. It is not necessary here to 

 discuss in detail the relationship of this assemblage tJ vulgaris, since this has been done 

 elsewhere. It should here be noted, however, that in considering this group as a whole, 

 certain forms of vulgaris come the nearest to representing the original primitive stock. 

 This is because each of the others possesses certain features indicative of an extreme 

 development along one or more lines. Therefore none of them can be considered as 

 primitive. It seems either that the earlier evolutionary stages have entirely disappeared, 

 or that they have not as yet been discovered by botanical collectors. Although this 

 dropping out of the earlier forms has resulted in the production of some 5 rather sharply 

 defined and non-overlapping species — or more if Asiatic forms are taken into account — it 

 is not to be assumed that these are widely separated phylogenetically, or that all can be 

 defined with absolute certainty. On the contrary, some of them differ from certain 

 subspecies of vulgaris only by features so subtle that a close phylogenetic analysis is 

 necessary in order to retain them in specific rank. Thus, for example, A. parryi closely 

 simulates A. vulgaris discolor and A. v. lindleyana, yet from its geographic distribution 

 and morphologic characters it is seen that its connection with vulgaris stock is not 

 through these specialized varieties, but through more primitive forms probably now 

 extinct. While the other enumerated species are of close kin to vulgaris, all can 

 similarly be shown to belong to lines which diverged from the parent stock before the 

 numerous subdivisions of this species began to differentiate. 



Artemisia vulgaris is the most variable of all the Artemisias, at least as far as the Amer- 

 ican species are concerned. When the subspecies are arranged in what appears to be a 

 natural phylogenetic sequence, as is attempted in the accompanying diagram, it is seen 

 that, although the extremes are far apart, all are so closely held together by forms repre- 

 senting intermediate steps that no place is found where a line can be drawn that will 

 separate the multitude of forms into well-defined species. This condition is not so re- 

 markable, however, when it is noted that the variations are not in essential features but 

 chiefly in characters of foliage, size of heads, number of flowers, and amount of pubes- 

 cence. Some of the resultant variations are very unlike in appearance, but it is not 

 difficult to see how all have had a common origin in no far distant past. As an aid to 

 this it should be remembered that not all of the known forms are indicated on the chart, 

 but only those which are sufficiently noteworthy to be ranked as subspecies. Between 

 many of these, still smaller variations are known, most of which are enumerated in the 

 text under the heading of "Minor variations." These represent the still shorter steps 

 in the progress of evolution within the species. Nearly all of them, as well as all of the 

 accepted subspecies, have at one time or another been classed as distinct species, so that 

 in all some 80 described units, as well as many more undescribed ones, are available for 

 study. It is thus seen that Artemisia vulgaris offers one of the most promising fields 

 for phylogenetic researches. In some portions of this field all intermediate stages are 

 still available, so that even the direction of evolution can be worked out with a reasonable 

 degree of certainty by means of field observations, mapping of distribution, and statis- 

 tical analyses. In other places small gaps occur. In some instances these have been 

 bridged through the production of the intermediate stages by experimental methods. 

 In only a few places are the lines of descent so broken that they can not be satisfactorily 



