A. VULGARIS. 93 



than. northern ones. This does not apply to coastal plants, since in these the leaves are 

 for the most part deeply pinnatifid. These facts are in accord with the general theory 

 that as the species extends towards the south or away from the coast the foliage is 

 reduced in size and simplified in its lobing. Even in those forms of heterophylla which 

 have undergone the greatest amount of modification in foliage characters, the leaves are 

 still ample as compared with those of ludoviciana and other varieties of dry, interior habi- 

 tats. In this connection it should be noted that, while heterophylla often grows in warm, 

 arid districts, it there occupies stream-banks, bottom-lands, and other places where there 

 is a reasonable amount of soil moisture to draw upon. As to the nature of the lobing 

 of the foliage, this varies through all degrees from deeply pinnatifid with widely spreading 

 and narrow lobes to entire. Often a peculiar cut will be observed in all of the principal 

 leaves of one clump of plants, while an entirely different type will be found on neighbor- 

 ing plants. This seems to indicate the presence of numerous strains, possibly with hybrids 

 between them. Apparently the only rational way of organizing these leaf-forms is by 

 the method of genetic analysis. Any attempt to classify them by usual taxonomic 

 methods would lead only to confusion, and it is because of the recognition of this that the 

 numerous so-called species of some recent works, based upon leaf-characters alone, are 

 here relegated to the category of minor variations. A hint as to what may be expected 

 in the way of leaf-forms is given in figure 3, p. 41, and figure 7, p. 74. 



In strong contrast to the trivial variations just discussed is the subspecies litoralis, 

 a form restricted to the vicinity of the coast from southern British Columbia to Mendocino 

 County, California. It differs from subspecies heterophylla, of which it is a derivative, 

 especially in the narrowed, shining involucre and in the reduced number of flowers. 

 Although the collections have been numerous, no intermediate forms have been encoun- 

 tered. The absence of overlapping in the number of flowers is indicated in table 6, and 

 the two may be distinguished without hesitation by an examination of the involucre 

 alone. 



The remaining subspecies differ from those thus far discussed in the usually smaller 

 heads which have a reduced number of flowers. Their leaves are comparatively narrow and 

 only once pinnatifid or toothed or often entire. This seems to be a natural group which 

 has originated from the tilesi stock and, spreading out over a large area to the southeast 

 of the range of that primitive form, has now come to occupy the Rocky Mountain region 

 especially, but with extensions southward through Mexico, east to slightly beyond the 

 Mississippi River, and west almost to the Pacific Coast. This westward extension, 

 however, is much less important than the others, since the group is not strongly repre- 

 sented west of the Great Basin. During the course of its occupancy of this extensive 

 area, and perhaps because of the wide range of conditions here encountered, the group 

 broke up into an innumerable series of forms, many of which have been accorded specific 

 rank by taxonomists. All of these so-called species are based upon highly variable 

 characters, such as those of the foliage, inflorescence, pubescence, etc. Many of them 

 are here mentioned only under minor variations, and some of the less important and 

 unnamed ones are not mentioned at all, while those which seem to represent definite 

 stages in the development of the species, or centers about which the minor variations 

 may be grouped, are treated as subspecies. Even these accepted subspecies are some- 

 times so closely interlocking in their characters that the evolutionary lines can not be 

 worked out with certainty at this time. This portion of the chart is therefore presented 

 more for the purpose of indicating the characters used than to show phyletic lines. 



The original form, which in turn gave rise to the others of this group, seems to have 

 been something now included under the subspecies ludoviciana. The derivation of the 

 othera from this can be accounted for in accordance with the laws of phylogeny (see 



