8 THE PHYLOGENETIC METHOD IN TAXONOMY. 



It is the essence of a system to organize knowledge, and the conversion of generic sec- 

 tions into genera conceals their inherent relationship. The most striking feature of 

 memory is its necessity for relating things to each other, and the multiplication of 

 small genera without evident relationship to each other greatly increases the labor 

 involved in remembering them, often to the degree that the worker can not or will not 

 utilize them. The argument that generic segregates should be adopted in justice to 

 the authors concerned, since they are quite as good as some accepted genera, is possible 

 only because of the failure to realize that synthesis and not analysis is the corner-stone 

 of classification. The question of justice is entirely subordinate to the demands of 

 evolution and phylogeny, and it is certain that these can not be met by segregation 

 of the usual sort. 



It is clearly recognized that the making of new genera is purely a matter of personal 

 judgment at the present time, and that this is profoundly affected by training and 

 environment, and especially by prejudices in favor of uniformity, segregation, etc. 

 There is no general agreement as to criteria, methods, or results, and the importance 

 of evolution as the one safe guide is rarely if ever considered. A knowledge of the genus 

 as a whole, especially when it includes exotic species, is too often lacking, and little or 

 no thought is given to the phylogeny of the genus and its sections in relation to genera 

 of the same evolutionary stock. More serious still is the all but inevitable magnifying 

 of criteria in the detached herbarium study of a group or genus and the consequent 

 lowering of the criteria for genera. The first cycle of this sort is nearing a close for lack 

 of material for segregation, and it is confidently to be expected that the next generation 

 will see a new lowering of criteria and a corresponding avalanche of segregates. This 

 can be avoided only by a stern insistence on the part of conservative taxonomists, 

 and- of all non-taxonomists, that changes in generic concepts must be based upon evolu- 

 tion, and made only after the fullest statistical and experimental studies. An augury 

 of the future of descriptive botany is furnished by the case of Astragalus, in which 

 Homalobus, one of the 18 segregates, already has almost as many so-called species as 

 the ecological treatment recognizes for the entire genus in North America. 



With respect to usability, the segregation of genera is especially unfortunate. It is 

 impossible for most botanists and practically all laymen to determine a large number 

 of the generic segregates without recourse to the herbarium, and their recognition in 

 the field is practically out of the question for all but the specialists in the group concerned. 

 Ready recognition means carrying the distinctive criteria in mind, and only the specialist 

 can hope to know the names of the segregates, to say nothing of their characters. More- 

 over, there is a definite limit to the number of names the taxonomist himself can readily 

 command, and this Umit is quickly reached with the great majority of those who use 

 taxonomy merely as a tool. If the actual genera of the pea family are to be known 

 and recognized on sight, it becomes a mental impossibility to deal with Astragalus when 

 split into 19 parts. When the same process is carried into scores of genera, a working 

 knowledge of flowering plants becomes impossible for anyone but the taxonomist, and 

 it is possible for him only in the restricted groups with which he is working. As a con- 

 sequence, taxonomy becomes an object of ridicule to those who would use it and can 

 not, and this feeling is extended to the whole subject of botany by the layman, who 

 properly looks upon the naming of plants as the first step in botanical knowledge. 



Proper treatment of genera. — It has repeatedly been emphasized that the treatment 

 of genera must be based upon evolution and phylogeny. This means the retention 

 of the vast majority of genera as recognized by Linnaeus, Bentham, Gray, and others, 

 together with the recognition of the subgenus or section as an essential unit for recording 

 the course of evolution. From the evolutionary standpoint, this requires the replacing 

 of generic segregates in their original genera, except in the rare cases where the genus 



