Abstract:The present paper made a brief introduction to the two current major species concepts and the various types of "species" existent in nature. The auther emphatically pointed out that in any case species are heterogeneous instead of homogeneous. Thus pharmacognostists should not be content with mere identification of the scientific names of plants, but are obligated to find out the intraspecific variations associated with pharmacognostic identification and to bring to light the regularities of formation, accumulation and dynamic changes of secondary metabolic products for medical use.