12 THE PHYLOGENETIC METHOD IN TAXONOMY. 



a complete range of individual and specific variation, with thoroughgoing ecological 

 analysis and statistical studies of the amount and direction of variation, is practically 

 unknown. The usual practice has had its justification in the past, when actual species 

 were still to be described, as shown by the results of Pursh, Nuttall, Torrey, Gray, and 

 others, and these reasons still obtain in lands little known botanically, especially the 

 tropics. For North America, however, the great majority of real species had been 

 described by the close of Gray's work, and the vast increase of species since that time 

 chiefly represents a change of personal views as to the criteria that mark this unit. 



While there has been an unfortunate shifting of standards in descriptive botany 

 generally, as shown by the almost universal raising of varieties to species (table 1), 

 much of the existing confusion is due to the lack of sympathy and understanding shown 

 by botanists toward the trinomial. It is probable that many segregators recognize that 

 most of their new forms are not actual species at all, but the prevailing botanical atti- 

 tude toward trinomials, and the failure of at least one code to give varietal names 

 nomenclatorial standing, have discouraged thinking in relationships, since this demanded 

 the use of the trinomial. The inconvenience of the latter is much more than offset by 

 its value in relating forms to the specific stock, as is proven by the practice of mam- 

 malogists and ornithologists in particular. However, while it is quite possible that 

 descriptive botanists have felt some compulsion toward the apparent simplicity and 

 uniformity of the binomial, it seems certain that the general botanist would have found 

 no more inconvenience in the use of trinomials than the zoologist, had he been given 

 the opportunity. 



Failures of specific segregation. — The segregation of species has practically all the 

 disadvantages of generic segregation, and in addition some that are peculiar to it. Sub- 

 jectively, it suffers critically from the inevitable lack of proper and adequate material, 

 owing to its being confined to the herbarium. Even more serious is the fact that segre- 

 gation is merely a matter of personal judgment, and makes use of none of the objective 

 checks, such as statistics and experiment. As already indicated, there is a successive 

 shifting of the standards for criteria, with the result that these always become lower in 

 quantitative terms, and never higher. Not only do the standards differ from indivi- 

 dual to individual, but sometimes they also change rapidly in the case of the same 

 individual. This is unavoidable as long as personal judgment is the only process involved, 

 and the continuance of this as the sole test will complete the existing chaos in another 

 decade. 



From the standpoint of one who must make use of the results, the greatest harm done 

 by segregation arises from its treatment of all forms as species, and hence as equivalent. 

 This is inconvenient enough in ordinary use, but it becomes fatal in all those cases where 

 relationship is of more importance than the mere name. These constitute practically 

 all the scientific and practical uses of plants, in which genetic relationship arising out 

 of evolution is a matter of primary concern. In short, segregation is unscientific because 

 it is unnatural and impracticable as to results, on account of its ignoring relationship. 

 The second great disadvantage of segregation lies in the practical impossibility of recog- 

 nizing most segregates in the field. This is a fatal difficulty in the case of all students 

 of vegetation, whether ecologists or practical scientists, such as foresters, grazing 

 experts, etc. The determination of the great majority of segregates can be made only 

 in the herbarium, if at all, and frequently fails of application in the midst of the wealth 

 of material in the field. 



In the enormous increase of unrelated forms treated as species, segregation constantly 

 destroys existing knowledge and fails to add anything new scientifically. Of the 

 thousands who make use of systematic botany, not even the specialist has the time or 

 ability to adjust his knowledge to each new segregation, and the general botanist or 



