Specific and infraspecific delimitation

In the hierarchic structure of the plant kingdom the species is, in the ranks of taxa, the most important entity. In comparison with the other ranks it is the one which is most distinct in nature to human and animal observation. The species are the most important building-stones of living matter. Huxley rightly agrees with Timofeeff-Ressovski (4, p. 3-4) in saying:—“that species have a greater reality in nature, or a greater degree of objectivity, than higher taxonomic categories. Species are in the majority definable as distinct self-perpetuating units with objective existence in nature, and therefore are on a different theoretical footing from genera and families or higher categories, which are not definable in this concrete way”.