V. GRANT 43 



with a definite geographical range. The result, of course, is that 

 many named species are equivalent to the geographical races of 

 a polytypic species. There are also a few botanists who adopt the 

 so-called biological species concept. 



The opinion held by many botanists today that the species is 

 undefinable is in part a heritage from the interregnum of the 

 typological species concept. This agnosticism is written into the 

 International Code of Botanical Nomenclature which through 

 four editions has studiously refrained from defining the species. 

 If one is operating within the framework of a typological species 

 concept, this attitude is certainly justified. 



The species which is defined on the basis of a certain number 

 and degree of morphological differences is indeed a subjectively 

 defined entity. No criterion of the amount of morphological dif- 

 ference between two forms that marks them as species, rather 

 than as subspecies, sections, or genera, etc., and that is capable 

 of application generally has ever been proposed. It follows that 

 different observers confronted with the same range of variation 

 in a series of specimens will frequently be unable to agree on 

 the taxonomic disposition of the case, in so far as their decisions 

 are predicated on a typological species concept. That such differ- 

 ences of opinion are commonplace is evident to anyone who has 

 compared different taxonomic treatments of the same group pre- 

 pared by different but equally well qualified authors. 



It is generally agreed by the adherents of both the typological 

 and the biological species concepts that the species of the typo- 

 logical concept can be defined only as that entity which a com- 

 petent systematist regards as a species. This conclusion consti- 

 tutes the strongest argument against retaining the typological 

 species concept in taxonomy, now that an objectively defined 

 concept is available to take its place. Unfortunately, the advo- 

 cates of the subjectivity of the species as a unit usually ignore 

 the existence of the biological definition. Thus Mason writes that, 

 "I have seen no putative definition of a taxonomic category so 

 worded as to be incapable of application either to the next higher 

 or the next lower category of the taxonomic structure. That 

 which is a species to one taxonomist may be a subspecies to 



