Volume 30 of the Flora of the U.S.S.R. contains descriptions of the species of the genus Hieracium L., the last genus in the system of classification of the family Compositae Giseke (~Asteraceae Dumort.). Extraordinary difficulty is experienced in dealing with the taxonomy of the genus because of the apomictic reproduction characteristic of the great majority of its species. Such a difficulty is enhanced by the absence of any contemporary survey of the native flora, as also of literature on the hawkweeds, in general.
A. Ya. Juxip made a special study of the hawkweeds of the northwest of the European part of the U.S.S.R. for many years and took upon himself the major trouble for studying all the accumulated materials of the hawkweeds in a revisionary context for the whole territory of the Soviet Union. The result of his efforts is the thirtieth volume of the Flora of U.S.S.R.. It contains descriptions of 785 species of the hawkweeds, including about 140 species described here for the first time. lt represents the first complete survey of the hawkweeds of th U.S.S.R. Its publication opens up the possibility of a serious study of the native species of hawkweeds, particularly of the regional floras, as a priority item.
In accordance with the traditional treatment of the genus Hieracium L., such units as were established initially as subspecies, are raised here to the rank of species. To a certain extent, this may violate the existing rules of nomenclature, but, in the present case, it is very convenient and practical. It may, however, be pointed out that some impreciseness does exist at present both in the definition of the first supra-specific categories SERIES (CYCLES) recognised in Hieracium, L. and in their nomenclature.